Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

11 files changed, 7414 insertions, 0 deletions

diff --git a/net/l2tp/Kconfig b/net/l2tp/Kconfig
new file mode 100644
index 000000000..b7856748e
--- /dev/null
+++ b/net/l2tp/Kconfig
@@ -0,0 +1,110 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# 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..cf8f27071
--- /dev/null
+++ b/net/l2tp/Makefile
@@ -0,0 +1,18 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the L2TP.
+#
+
+obj-$(CONFIG_L2TP) += l2tp_core.o
+
+CFLAGS_l2tp_core.o += -I$(src)
+
+# 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..8d21ff25f
--- /dev/null
+++ b/net/l2tp/l2tp_core.c
@@ -0,0 +1,1723 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* 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)
+ */
+
+#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"
+#include "trace.h"
+
+#define CREATE_TRACE_POINTS
+#include "trace.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_MAX		14
+
+/* 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 struct workqueue_struct *l2tp_wq;
+
+/* per-net private data for this module */
+static unsigned int l2tp_net_id;
+struct l2tp_net {
+	/* Lock for write access to l2tp_tunnel_idr */
+	spinlock_t l2tp_tunnel_idr_lock;
+	struct idr l2tp_tunnel_idr;
+	struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];
+	/* Lock for write access to l2tp_session_hlist */
+	spinlock_t l2tp_session_hlist_lock;
+};
+
+#if IS_ENABLED(CONFIG_IPV6)
+static bool l2tp_sk_is_v6(struct sock *sk)
+{
+	return sk->sk_family == PF_INET6 &&
+	       !ipv6_addr_v4mapped(&sk->sk_v6_daddr);
+}
+#endif
+
+static inline struct l2tp_net *l2tp_pernet(const struct net *net)
+{
+	return net_generic(net, l2tp_net_id);
+}
+
+/* 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)];
+}
+
+/* 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)];
+}
+
+static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
+{
+	trace_free_tunnel(tunnel);
+	sock_put(tunnel->sock);
+	/* the tunnel is freed in the socket destructor */
+}
+
+static void l2tp_session_free(struct l2tp_session *session)
+{
+	trace_free_session(session);
+	if (session->tunnel)
+		l2tp_tunnel_dec_refcount(session->tunnel);
+	kfree(session);
+}
+
+struct l2tp_tunnel *l2tp_sk_to_tunnel(struct sock *sk)
+{
+	struct l2tp_tunnel *tunnel = sk->sk_user_data;
+
+	if (tunnel)
+		if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC))
+			return NULL;
+
+	return tunnel;
+}
+EXPORT_SYMBOL_GPL(l2tp_sk_to_tunnel);
+
+void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel)
+{
+	refcount_inc(&tunnel->ref_count);
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_inc_refcount);
+
+void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel)
+{
+	if (refcount_dec_and_test(&tunnel->ref_count))
+		l2tp_tunnel_free(tunnel);
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_dec_refcount);
+
+void l2tp_session_inc_refcount(struct l2tp_session *session)
+{
+	refcount_inc(&session->ref_count);
+}
+EXPORT_SYMBOL_GPL(l2tp_session_inc_refcount);
+
+void l2tp_session_dec_refcount(struct l2tp_session *session)
+{
+	if (refcount_dec_and_test(&session->ref_count))
+		l2tp_session_free(session);
+}
+EXPORT_SYMBOL_GPL(l2tp_session_dec_refcount);
+
+/* Lookup a tunnel. A new reference is held on the returned tunnel. */
+struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id)
+{
+	const struct l2tp_net *pn = l2tp_pernet(net);
+	struct l2tp_tunnel *tunnel;
+
+	rcu_read_lock_bh();
+	tunnel = idr_find(&pn->l2tp_tunnel_idr, tunnel_id);
+	if (tunnel && refcount_inc_not_zero(&tunnel->ref_count)) {
+		rcu_read_unlock_bh();
+		return tunnel;
+	}
+	rcu_read_unlock_bh();
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_get);
+
+struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth)
+{
+	struct l2tp_net *pn = l2tp_pernet(net);
+	unsigned long tunnel_id, tmp;
+	struct l2tp_tunnel *tunnel;
+	int count = 0;
+
+	rcu_read_lock_bh();
+	idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) {
+		if (tunnel && ++count > nth &&
+		    refcount_inc_not_zero(&tunnel->ref_count)) {
+			rcu_read_unlock_bh();
+			return tunnel;
+		}
+	}
+	rcu_read_unlock_bh();
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_get_nth);
+
+struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel,
+					     u32 session_id)
+{
+	struct hlist_head *session_list;
+	struct l2tp_session *session;
+
+	session_list = l2tp_session_id_hash(tunnel, session_id);
+
+	rcu_read_lock_bh();
+	hlist_for_each_entry_rcu(session, session_list, hlist)
+		if (session->session_id == session_id) {
+			l2tp_session_inc_refcount(session);
+			rcu_read_unlock_bh();
+
+			return session;
+		}
+	rcu_read_unlock_bh();
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_get_session);
+
+struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id)
+{
+	struct hlist_head *session_list;
+	struct l2tp_session *session;
+
+	session_list = l2tp_session_id_hash_2(l2tp_pernet(net), session_id);
+
+	rcu_read_lock_bh();
+	hlist_for_each_entry_rcu(session, session_list, global_hlist)
+		if (session->session_id == session_id) {
+			l2tp_session_inc_refcount(session);
+			rcu_read_unlock_bh();
+
+			return session;
+		}
+	rcu_read_unlock_bh();
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(l2tp_session_get);
+
+struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth)
+{
+	int hash;
+	struct l2tp_session *session;
+	int count = 0;
+
+	rcu_read_lock_bh();
+	for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
+		hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) {
+			if (++count > nth) {
+				l2tp_session_inc_refcount(session);
+				rcu_read_unlock_bh();
+				return session;
+			}
+		}
+	}
+
+	rcu_read_unlock_bh();
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(l2tp_session_get_nth);
+
+/* Lookup a session by interface name.
+ * This is very inefficient but is only used by management interfaces.
+ */
+struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
+						const 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)) {
+				l2tp_session_inc_refcount(session);
+				rcu_read_unlock_bh();
+
+				return session;
+			}
+		}
+	}
+
+	rcu_read_unlock_bh();
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(l2tp_session_get_by_ifname);
+
+int l2tp_session_register(struct l2tp_session *session,
+			  struct l2tp_tunnel *tunnel)
+{
+	struct l2tp_session *session_walk;
+	struct hlist_head *g_head;
+	struct hlist_head *head;
+	struct l2tp_net *pn;
+	int err;
+
+	head = l2tp_session_id_hash(tunnel, session->session_id);
+
+	spin_lock_bh(&tunnel->hlist_lock);
+	if (!tunnel->acpt_newsess) {
+		err = -ENODEV;
+		goto err_tlock;
+	}
+
+	hlist_for_each_entry(session_walk, head, hlist)
+		if (session_walk->session_id == session->session_id) {
+			err = -EEXIST;
+			goto err_tlock;
+		}
+
+	if (tunnel->version == L2TP_HDR_VER_3) {
+		pn = l2tp_pernet(tunnel->l2tp_net);
+		g_head = l2tp_session_id_hash_2(pn, session->session_id);
+
+		spin_lock_bh(&pn->l2tp_session_hlist_lock);
+
+		/* IP encap expects session IDs to be globally unique, while
+		 * UDP encap doesn't.
+		 */
+		hlist_for_each_entry(session_walk, g_head, global_hlist)
+			if (session_walk->session_id == session->session_id &&
+			    (session_walk->tunnel->encap == L2TP_ENCAPTYPE_IP ||
+			     tunnel->encap == L2TP_ENCAPTYPE_IP)) {
+				err = -EEXIST;
+				goto err_tlock_pnlock;
+			}
+
+		l2tp_tunnel_inc_refcount(tunnel);
+		hlist_add_head_rcu(&session->global_hlist, g_head);
+
+		spin_unlock_bh(&pn->l2tp_session_hlist_lock);
+	} else {
+		l2tp_tunnel_inc_refcount(tunnel);
+	}
+
+	hlist_add_head_rcu(&session->hlist, head);
+	spin_unlock_bh(&tunnel->hlist_lock);
+
+	trace_register_session(session);
+
+	return 0;
+
+err_tlock_pnlock:
+	spin_unlock_bh(&pn->l2tp_session_hlist_lock);
+err_tlock:
+	spin_unlock_bh(&tunnel->hlist_lock);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(l2tp_session_register);
+
+/*****************************************************************************
+ * 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);
+			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;
+		trace_session_seqnum_update(session);
+	}
+
+	/* call private receive handler */
+	if (session->recv_skb)
+		(*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
+	else
+		kfree_skb(skb);
+}
+
+/* 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) {
+		struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb);
+
+		/* If the packet has been pending on the queue for too long, discard it */
+		if (time_after(jiffies, cb->expires)) {
+			atomic_long_inc(&session->stats.rx_seq_discards);
+			atomic_long_inc(&session->stats.rx_errors);
+			trace_session_pkt_expired(session, cb->ns);
+			session->reorder_skip = 1;
+			__skb_unlink(skb, &session->reorder_q);
+			kfree_skb(skb);
+			continue;
+		}
+
+		if (cb->has_seq) {
+			if (session->reorder_skip) {
+				session->reorder_skip = 0;
+				session->nr = cb->ns;
+				trace_session_seqnum_reset(session);
+			}
+			if (cb->ns != session->nr)
+				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)
+{
+	struct l2tp_skb_cb *cb = L2TP_SKB_CB(skb);
+
+	if (!l2tp_seq_check_rx_window(session, cb->ns)) {
+		/* Packet sequence number is outside allowed window.
+		 * Discard it.
+		 */
+		trace_session_pkt_outside_rx_window(session, cb->ns);
+		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 (cb->ns == session->nr) {
+		skb_queue_tail(&session->reorder_q, skb);
+	} else {
+		u32 nr_oos = cb->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;
+		}
+		if (!session->reorder_skip) {
+			atomic_long_inc(&session->stats.rx_seq_discards);
+			trace_session_pkt_oos(session, cb->ns);
+			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 and sublayer format 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)
+{
+	struct l2tp_tunnel *tunnel = session->tunnel;
+	int offset;
+
+	/* Parse and check optional cookie */
+	if (session->peer_cookie_len > 0) {
+		if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
+			pr_debug_ratelimited("%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.
+	 */
+	L2TP_SKB_CB(skb)->has_seq = 0;
+	if (tunnel->version == L2TP_HDR_VER_2) {
+		if (hdrflags & L2TP_HDRFLAG_S) {
+			/* Store L2TP info in the skb */
+			L2TP_SKB_CB(skb)->ns = ntohs(*(__be16 *)ptr);
+			L2TP_SKB_CB(skb)->has_seq = 1;
+			ptr += 2;
+			/* Skip past nr in the header */
+			ptr += 2;
+
+		}
+	} else if (session->l2specific_type == L2TP_L2SPECTYPE_DEFAULT) {
+		u32 l2h = ntohl(*(__be32 *)ptr);
+
+		if (l2h & 0x40000000) {
+			/* Store L2TP info in the skb */
+			L2TP_SKB_CB(skb)->ns = l2h & 0x00ffffff;
+			L2TP_SKB_CB(skb)->has_seq = 1;
+		}
+		ptr += 4;
+	}
+
+	if (L2TP_SKB_CB(skb)->has_seq) {
+		/* Received a packet with sequence numbers. If we're the LAC,
+		 * check if we sre sending sequence numbers and if not,
+		 * configure it so.
+		 */
+		if (!session->lns_mode && !session->send_seq) {
+			trace_session_seqnum_lns_enable(session);
+			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) {
+			pr_debug_ratelimited("%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) {
+			trace_session_seqnum_lns_disable(session);
+			session->send_seq = 0;
+			l2tp_session_set_header_len(session, tunnel->version);
+		} else if (session->send_seq) {
+			pr_debug_ratelimited("%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 defined only for L2TPv2 and is
+	 * indicated by an optional 16-bit value in the header.
+	 */
+	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;
+		}
+	}
+
+	offset = ptr - optr;
+	if (!pskb_may_pull(skb, offset))
+		goto discard;
+
+	__skb_pull(skb, offset);
+
+	/* 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);
+
+	return;
+
+discard:
+	atomic_long_inc(&session->stats.rx_errors);
+	kfree_skb(skb);
+}
+EXPORT_SYMBOL_GPL(l2tp_recv_common);
+
+/* Drop skbs from the session's reorder_q
+ */
+static void l2tp_session_queue_purge(struct l2tp_session *session)
+{
+	struct sk_buff *skb = NULL;
+
+	while ((skb = skb_dequeue(&session->reorder_q))) {
+		atomic_long_inc(&session->stats.rx_errors);
+		kfree_skb(skb);
+	}
+}
+
+/* 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)
+{
+	struct l2tp_session *session = NULL;
+	unsigned char *ptr, *optr;
+	u16 hdrflags;
+	u32 tunnel_id, session_id;
+	u16 version;
+	int length;
+
+	/* UDP has verified checksum */
+
+	/* UDP always verifies the packet length. */
+	__skb_pull(skb, sizeof(struct udphdr));
+
+	/* Short packet? */
+	if (!pskb_may_pull(skb, L2TP_HDR_SIZE_MAX)) {
+		pr_debug_ratelimited("%s: recv short packet (len=%d)\n",
+				     tunnel->name, skb->len);
+		goto invalid;
+	}
+
+	/* Point to L2TP header */
+	optr = skb->data;
+	ptr = skb->data;
+
+	/* Get L2TP header flags */
+	hdrflags = ntohs(*(__be16 *)ptr);
+
+	/* Check protocol version */
+	version = hdrflags & L2TP_HDR_VER_MASK;
+	if (version != tunnel->version) {
+		pr_debug_ratelimited("%s: recv protocol version mismatch: got %d expected %d\n",
+				     tunnel->name, version, tunnel->version);
+		goto invalid;
+	}
+
+	/* Get length of L2TP packet */
+	length = skb->len;
+
+	/* If type is control packet, it is handled by userspace. */
+	if (hdrflags & L2TP_HDRFLAG_T)
+		goto pass;
+
+	/* 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_tunnel_get_session(tunnel, session_id);
+	if (!session || !session->recv_skb) {
+		if (session)
+			l2tp_session_dec_refcount(session);
+
+		/* Not found? Pass to userspace to deal with */
+		pr_debug_ratelimited("%s: no session found (%u/%u). Passing up.\n",
+				     tunnel->name, tunnel_id, session_id);
+		goto pass;
+	}
+
+	if (tunnel->version == L2TP_HDR_VER_3 &&
+	    l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) {
+		l2tp_session_dec_refcount(session);
+		goto invalid;
+	}
+
+	l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
+	l2tp_session_dec_refcount(session);
+
+	return 0;
+
+invalid:
+	atomic_long_inc(&tunnel->stats.rx_invalid);
+
+pass:
+	/* 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;
+
+	/* Note that this is called from the encap_rcv hook inside an
+	 * RCU-protected region, but without the socket being locked.
+	 * Hence we use rcu_dereference_sk_user_data to access the
+	 * tunnel data structure rather the usual l2tp_sk_to_tunnel
+	 * accessor function.
+	 */
+	tunnel = rcu_dereference_sk_user_data(sk);
+	if (!tunnel)
+		goto pass_up;
+	if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC))
+		goto pass_up;
+
+	if (l2tp_udp_recv_core(tunnel, skb))
+		goto pass_up;
+
+	return 0;
+
+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;
+		trace_session_seqnum_update(session);
+	}
+
+	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_type == L2TP_L2SPECTYPE_DEFAULT) {
+		u32 l2h = 0;
+
+		if (session->send_seq) {
+			l2h = 0x40000000 | session->ns;
+			session->ns++;
+			session->ns &= 0xffffff;
+			trace_session_seqnum_update(session);
+		}
+
+		*((__be32 *)bufp) = htonl(l2h);
+		bufp += 4;
+	}
+
+	return bufp - optr;
+}
+
+/* Queue the packet to IP for output: tunnel socket lock must be held */
+static int l2tp_xmit_queue(struct l2tp_tunnel *tunnel, struct sk_buff *skb, struct flowi *fl)
+{
+	int err;
+
+	skb->ignore_df = 1;
+	skb_dst_drop(skb);
+#if IS_ENABLED(CONFIG_IPV6)
+	if (l2tp_sk_is_v6(tunnel->sock))
+		err = inet6_csk_xmit(tunnel->sock, skb, NULL);
+	else
+#endif
+		err = ip_queue_xmit(tunnel->sock, skb, fl);
+
+	return err >= 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
+}
+
+static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, unsigned int *len)
+{
+	struct l2tp_tunnel *tunnel = session->tunnel;
+	unsigned int data_len = skb->len;
+	struct sock *sk = tunnel->sock;
+	int headroom, uhlen, udp_len;
+	int ret = NET_XMIT_SUCCESS;
+	struct inet_sock *inet;
+	struct udphdr *uh;
+
+	/* 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.
+	 */
+	uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(*uh) : 0;
+	headroom = NET_SKB_PAD + sizeof(struct iphdr) + uhlen + session->hdr_len;
+	if (skb_cow_head(skb, headroom)) {
+		kfree_skb(skb);
+		return NET_XMIT_DROP;
+	}
+
+	/* Setup L2TP header */
+	if (tunnel->version == L2TP_HDR_VER_2)
+		l2tp_build_l2tpv2_header(session, __skb_push(skb, session->hdr_len));
+	else
+		l2tp_build_l2tpv3_header(session, __skb_push(skb, session->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_ct(skb);
+
+	bh_lock_sock_nested(sk);
+	if (sock_owned_by_user(sk)) {
+		kfree_skb(skb);
+		ret = NET_XMIT_DROP;
+		goto out_unlock;
+	}
+
+	/* The user-space may change the connection status for the user-space
+	 * provided socket at run time: we must check it under the socket lock
+	 */
+	if (tunnel->fd >= 0 && sk->sk_state != TCP_ESTABLISHED) {
+		kfree_skb(skb);
+		ret = NET_XMIT_DROP;
+		goto out_unlock;
+	}
+
+	/* Report transmitted length before we add encap header, which keeps
+	 * statistics consistent for both UDP and IP encap tx/rx paths.
+	 */
+	*len = skb->len;
+
+	inet = inet_sk(sk);
+	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 + session->hdr_len + data_len;
+		uh->len = htons(udp_len);
+
+		/* Calculate UDP checksum if configured to do so */
+#if IS_ENABLED(CONFIG_IPV6)
+		if (l2tp_sk_is_v6(sk))
+			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;
+	}
+
+	ret = l2tp_xmit_queue(tunnel, skb, &inet->cork.fl);
+
+out_unlock:
+	bh_unlock_sock(sk);
+
+	return ret;
+}
+
+/* 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)
+{
+	unsigned int len = 0;
+	int ret;
+
+	ret = l2tp_xmit_core(session, skb, &len);
+	if (ret == NET_XMIT_SUCCESS) {
+		atomic_long_inc(&session->tunnel->stats.tx_packets);
+		atomic_long_add(len, &session->tunnel->stats.tx_bytes);
+		atomic_long_inc(&session->stats.tx_packets);
+		atomic_long_add(len, &session->stats.tx_bytes);
+	} else {
+		atomic_long_inc(&session->tunnel->stats.tx_errors);
+		atomic_long_inc(&session->stats.tx_errors);
+	}
+	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_sk_to_tunnel(sk);
+
+	if (!tunnel)
+		goto end;
+
+	/* Disable udp encapsulation */
+	switch (tunnel->encap) {
+	case L2TP_ENCAPTYPE_UDP:
+		/* No longer an encapsulation socket. See net/ipv4/udp.c */
+		WRITE_ONCE(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 */
+	write_lock_bh(&sk->sk_callback_lock);
+	sk->sk_destruct = tunnel->old_sk_destruct;
+	sk->sk_user_data = NULL;
+	write_unlock_bh(&sk->sk_callback_lock);
+
+	/* Call the original destructor */
+	if (sk->sk_destruct)
+		(*sk->sk_destruct)(sk);
+
+	kfree_rcu(tunnel, rcu);
+end:
+	return;
+}
+
+/* Remove an l2tp session from l2tp_core's hash lists. */
+static 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 */
+		spin_lock_bh(&tunnel->hlist_lock);
+		hlist_del_init_rcu(&session->hlist);
+		spin_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();
+	}
+}
+
+/* When the tunnel is closed, all the attached sessions need to go too.
+ */
+static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
+{
+	struct l2tp_session *session;
+	int hash;
+
+	spin_lock_bh(&tunnel->hlist_lock);
+	tunnel->acpt_newsess = false;
+	for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
+again:
+		hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) {
+			hlist_del_init_rcu(&session->hlist);
+
+			spin_unlock_bh(&tunnel->hlist_lock);
+			l2tp_session_delete(session);
+			spin_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;
+		}
+	}
+	spin_unlock_bh(&tunnel->hlist_lock);
+}
+
+/* Tunnel socket destroy hook for UDP encapsulation */
+static void l2tp_udp_encap_destroy(struct sock *sk)
+{
+	struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
+
+	if (tunnel)
+		l2tp_tunnel_delete(tunnel);
+}
+
+static void l2tp_tunnel_remove(struct net *net, struct l2tp_tunnel *tunnel)
+{
+	struct l2tp_net *pn = l2tp_pernet(net);
+
+	spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
+	idr_remove(&pn->l2tp_tunnel_idr, tunnel->tunnel_id);
+	spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
+}
+
+/* Workqueue tunnel deletion function */
+static void l2tp_tunnel_del_work(struct work_struct *work)
+{
+	struct l2tp_tunnel *tunnel = container_of(work, struct l2tp_tunnel,
+						  del_work);
+	struct sock *sk = tunnel->sock;
+	struct socket *sock = sk->sk_socket;
+
+	l2tp_tunnel_closeall(tunnel);
+
+	/* If the tunnel socket was created within the kernel, use
+	 * the sk API to release it here.
+	 */
+	if (tunnel->fd < 0) {
+		if (sock) {
+			kernel_sock_shutdown(sock, SHUT_RDWR);
+			sock_release(sock);
+		}
+	}
+
+	l2tp_tunnel_remove(tunnel->l2tp_net, tunnel);
+	/* drop initial ref */
+	l2tp_tunnel_dec_refcount(tunnel);
+
+	/* drop workqueue ref */
+	l2tp_tunnel_dec_refcount(tunnel);
+}
+
+/* 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(net, AF_INET6, SOCK_DGRAM,
+					       IPPROTO_L2TP, &sock);
+			if (err < 0)
+				goto out;
+
+			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(net, AF_INET, SOCK_DGRAM,
+					       IPPROTO_L2TP, &sock);
+			if (err < 0)
+				goto out;
+
+			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);
+		sock_release(sock);
+		*sockp = NULL;
+	}
+
+	return err;
+}
+
+int l2tp_tunnel_create(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;
+	enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
+
+	if (cfg)
+		encap = cfg->encap;
+
+	tunnel = kzalloc(sizeof(*tunnel), GFP_KERNEL);
+	if (!tunnel) {
+		err = -ENOMEM;
+		goto err;
+	}
+
+	tunnel->version = version;
+	tunnel->tunnel_id = tunnel_id;
+	tunnel->peer_tunnel_id = peer_tunnel_id;
+
+	tunnel->magic = L2TP_TUNNEL_MAGIC;
+	sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
+	spin_lock_init(&tunnel->hlist_lock);
+	tunnel->acpt_newsess = true;
+
+	tunnel->encap = encap;
+
+	refcount_set(&tunnel->ref_count, 1);
+	tunnel->fd = fd;
+
+	/* Init delete workqueue struct */
+	INIT_WORK(&tunnel->del_work, l2tp_tunnel_del_work);
+
+	INIT_LIST_HEAD(&tunnel->list);
+
+	err = 0;
+err:
+	if (tunnelp)
+		*tunnelp = tunnel;
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
+
+static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
+				enum l2tp_encap_type encap)
+{
+	if (!net_eq(sock_net(sk), net))
+		return -EINVAL;
+
+	if (sk->sk_type != SOCK_DGRAM)
+		return -EPROTONOSUPPORT;
+
+	if (sk->sk_family != PF_INET && sk->sk_family != PF_INET6)
+		return -EPROTONOSUPPORT;
+
+	if ((encap == L2TP_ENCAPTYPE_UDP && sk->sk_protocol != IPPROTO_UDP) ||
+	    (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP))
+		return -EPROTONOSUPPORT;
+
+	if (sk->sk_user_data)
+		return -EBUSY;
+
+	return 0;
+}
+
+int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
+			 struct l2tp_tunnel_cfg *cfg)
+{
+	struct l2tp_net *pn = l2tp_pernet(net);
+	u32 tunnel_id = tunnel->tunnel_id;
+	struct socket *sock;
+	struct sock *sk;
+	int ret;
+
+	spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
+	ret = idr_alloc_u32(&pn->l2tp_tunnel_idr, NULL, &tunnel_id, tunnel_id,
+			    GFP_ATOMIC);
+	spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
+	if (ret)
+		return ret == -ENOSPC ? -EEXIST : ret;
+
+	if (tunnel->fd < 0) {
+		ret = l2tp_tunnel_sock_create(net, tunnel->tunnel_id,
+					      tunnel->peer_tunnel_id, cfg,
+					      &sock);
+		if (ret < 0)
+			goto err;
+	} else {
+		sock = sockfd_lookup(tunnel->fd, &ret);
+		if (!sock)
+			goto err;
+	}
+
+	sk = sock->sk;
+	lock_sock(sk);
+	write_lock_bh(&sk->sk_callback_lock);
+	ret = l2tp_validate_socket(sk, net, tunnel->encap);
+	if (ret < 0)
+		goto err_inval_sock;
+	rcu_assign_sk_user_data(sk, tunnel);
+	write_unlock_bh(&sk->sk_callback_lock);
+
+	if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
+		struct udp_tunnel_sock_cfg udp_cfg = {
+			.sk_user_data = tunnel,
+			.encap_type = UDP_ENCAP_L2TPINUDP,
+			.encap_rcv = l2tp_udp_encap_recv,
+			.encap_destroy = l2tp_udp_encap_destroy,
+		};
+
+		setup_udp_tunnel_sock(net, sock, &udp_cfg);
+	}
+
+	tunnel->old_sk_destruct = sk->sk_destruct;
+	sk->sk_destruct = &l2tp_tunnel_destruct;
+	sk->sk_allocation = GFP_ATOMIC;
+	release_sock(sk);
+
+	sock_hold(sk);
+	tunnel->sock = sk;
+	tunnel->l2tp_net = net;
+
+	spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
+	idr_replace(&pn->l2tp_tunnel_idr, tunnel, tunnel->tunnel_id);
+	spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
+
+	trace_register_tunnel(tunnel);
+
+	if (tunnel->fd >= 0)
+		sockfd_put(sock);
+
+	return 0;
+
+err_inval_sock:
+	write_unlock_bh(&sk->sk_callback_lock);
+	release_sock(sk);
+
+	if (tunnel->fd < 0)
+		sock_release(sock);
+	else
+		sockfd_put(sock);
+err:
+	l2tp_tunnel_remove(net, tunnel);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_register);
+
+/* This function is used by the netlink TUNNEL_DELETE command.
+ */
+void l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
+{
+	if (!test_and_set_bit(0, &tunnel->dead)) {
+		trace_delete_tunnel(tunnel);
+		l2tp_tunnel_inc_refcount(tunnel);
+		queue_work(l2tp_wq, &tunnel->del_work);
+	}
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
+
+void l2tp_session_delete(struct l2tp_session *session)
+{
+	if (test_and_set_bit(0, &session->dead))
+		return;
+
+	trace_delete_session(session);
+	l2tp_session_unhash(session);
+	l2tp_session_queue_purge(session);
+	if (session->session_close)
+		(*session->session_close)(session);
+
+	l2tp_session_dec_refcount(session);
+}
+EXPORT_SYMBOL_GPL(l2tp_session_delete);
+
+/* We come here whenever a session's send_seq, cookie_len or
+ * l2specific_type 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->hdr_len += l2tp_get_l2specific_len(session);
+		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(*session) + priv_size, GFP_KERNEL);
+	if (session) {
+		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);
+
+		if (cfg) {
+			session->pwtype = cfg->pw_type;
+			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->l2specific_type = cfg->l2specific_type;
+			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);
+		}
+
+		l2tp_session_set_header_len(session, tunnel->version);
+
+		refcount_set(&session->ref_count, 1);
+
+		return session;
+	}
+
+	return ERR_PTR(-ENOMEM);
+}
+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;
+
+	idr_init(&pn->l2tp_tunnel_idr);
+	spin_lock_init(&pn->l2tp_tunnel_idr_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;
+	unsigned long tunnel_id, tmp;
+	int hash;
+
+	rcu_read_lock_bh();
+	idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) {
+		if (tunnel)
+			l2tp_tunnel_delete(tunnel);
+	}
+	rcu_read_unlock_bh();
+
+	if (l2tp_wq)
+		flush_workqueue(l2tp_wq);
+	rcu_barrier();
+
+	for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)
+		WARN_ON_ONCE(!hlist_empty(&pn->l2tp_session_hlist[hash]));
+	idr_destroy(&pn->l2tp_tunnel_idr);
+}
+
+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..a88e070b4
--- /dev/null
+++ b/net/l2tp/l2tp_core.h
@@ -0,0 +1,346 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* L2TP internal definitions.
+ *
+ * Copyright (c) 2008,2009 Katalix Systems Ltd
+ */
+#include <linux/refcount.h>
+
+#ifndef _L2TP_CORE_H_
+#define _L2TP_CORE_H_
+
+#include <net/dst.h>
+#include <net/sock.h>
+
+#ifdef CONFIG_XFRM
+#include <net/xfrm.h>
+#endif
+
+/* Random numbers used for internal consistency checks of tunnel and session structures */
+#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	BIT(L2TP_HASH_BITS)
+
+/* System-wide session hash table size */
+#define L2TP_HASH_BITS_2	8
+#define L2TP_HASH_SIZE_2	BIT(L2TP_HASH_BITS_2)
+
+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;
+	atomic_long_t		rx_invalid;
+};
+
+struct l2tp_tunnel;
+
+/* L2TP session configuration */
+struct l2tp_session_cfg {
+	enum l2tp_pwtype	pw_type;
+	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 LNS control.
+						 */
+	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) */
+	char			*ifname;
+};
+
+/* Represents a session (pseudowire) instance.
+ * Tracks runtime state including cookies, dataplane packet sequencing, and IO statistics.
+ * Is linked into a per-tunnel session hashlist; and in the case of an L2TPv3 session into
+ * an additional per-net ("global") hashlist.
+ */
+#define L2TP_SESSION_NAME_MAX 32
+struct l2tp_session {
+	int			magic;		/* should be L2TP_SESSION_MAGIC */
+	long			dead;
+
+	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			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 */
+	refcount_t		ref_count;
+
+	char			name[L2TP_SESSION_NAME_MAX]; /* for logging */
+	char			ifname[IFNAMSIZ];
+	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 LNS control.
+						 */
+	int			reorder_timeout; /* configured reorder timeout (in jiffies) */
+	int			reorder_skip;	/* set if skip to next nr */
+	enum l2tp_pwtype	pwtype;
+	struct l2tp_stats	stats;
+	struct hlist_node	global_hlist;	/* global hash list node */
+
+	/* Session receive handler for data packets.
+	 * Each pseudowire implementation should implement this callback in order to
+	 * handle incoming packets.  Packets are passed to the pseudowire handler after
+	 * reordering, if data sequence numbers are enabled for the session.
+	 */
+	void (*recv_skb)(struct l2tp_session *session, struct sk_buff *skb, int data_len);
+
+	/* Session close handler.
+	 * Each pseudowire implementation may implement this callback in order to carry
+	 * out pseudowire-specific shutdown actions.
+	 * The callback is called by core after unhashing the session and purging its
+	 * reorder queue.
+	 */
+	void (*session_close)(struct l2tp_session *session);
+
+	/* Session show handler.
+	 * Pseudowire-specific implementation of debugfs session rendering.
+	 * The callback is called by l2tp_debugfs.c after rendering core session
+	 * information.
+	 */
+	void (*show)(struct seq_file *m, void *priv);
+
+	u8			priv[];		/* private data */
+};
+
+/* L2TP tunnel configuration */
+struct l2tp_tunnel_cfg {
+	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;
+};
+
+/* Represents a tunnel instance.
+ * Tracks runtime state including IO statistics.
+ * Holds the tunnel socket (either passed from userspace or directly created by the kernel).
+ * Maintains a hashlist of sessions belonging to the tunnel instance.
+ * Is linked into a per-net list of tunnels.
+ */
+#define L2TP_TUNNEL_NAME_MAX 20
+struct l2tp_tunnel {
+	int			magic;		/* Should be L2TP_TUNNEL_MAGIC */
+
+	unsigned long		dead;
+
+	struct rcu_head rcu;
+	spinlock_t		hlist_lock;	/* write-protection for session_hlist */
+	bool			acpt_newsess;	/* indicates whether this tunnel accepts
+						 * new sessions. Protected by hlist_lock.
+						 */
+	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[L2TP_TUNNEL_NAME_MAX]; /* for logging */
+	enum l2tp_encap_type	encap;
+	struct l2tp_stats	stats;
+
+	struct list_head	list;		/* list node on per-namespace list of tunnels */
+	struct net		*l2tp_net;	/* the net we belong to */
+
+	refcount_t		ref_count;
+	void (*old_sk_destruct)(struct sock *sk);
+	struct sock		*sock;		/* parent socket */
+	int			fd;		/* parent fd, if tunnel socket was created
+						 * by userspace
+						 */
+
+	struct work_struct	del_work;
+};
+
+/* Pseudowire ops callbacks for use with the l2tp genetlink interface */
+struct l2tp_nl_cmd_ops {
+	/* The pseudowire session create callback is responsible for creating a session
+	 * instance for a specific pseudowire type.
+	 * It must call l2tp_session_create and l2tp_session_register to register the
+	 * session instance, as well as carry out any pseudowire-specific initialisation.
+	 * It must return >= 0 on success, or an appropriate negative errno value on failure.
+	 */
+	int (*session_create)(struct net *net, struct l2tp_tunnel *tunnel,
+			      u32 session_id, u32 peer_session_id,
+			      struct l2tp_session_cfg *cfg);
+
+	/* The pseudowire session delete callback is responsible for initiating the deletion
+	 * of a session instance.
+	 * It must call l2tp_session_delete, as well as carry out any pseudowire-specific
+	 * teardown actions.
+	 */
+	void (*session_delete)(struct l2tp_session *session);
+};
+
+static inline void *l2tp_session_priv(struct l2tp_session *session)
+{
+	return &session->priv[0];
+}
+
+/* Tunnel and session refcounts */
+void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel);
+void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel);
+void l2tp_session_inc_refcount(struct l2tp_session *session);
+void l2tp_session_dec_refcount(struct l2tp_session *session);
+
+/* Tunnel and session lookup.
+ * These functions take a reference on the instances they return, so
+ * the caller must ensure that the reference is dropped appropriately.
+ */
+struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id);
+struct l2tp_tunnel *l2tp_tunnel_get_nth(const struct net *net, int nth);
+struct l2tp_session *l2tp_tunnel_get_session(struct l2tp_tunnel *tunnel,
+					     u32 session_id);
+
+struct l2tp_session *l2tp_session_get(const struct net *net, u32 session_id);
+struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth);
+struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
+						const char *ifname);
+
+/* Tunnel and session lifetime management.
+ * Creation of a new instance is a two-step process: create, then register.
+ * Destruction is triggered using the *_delete functions, and completes asynchronously.
+ */
+int l2tp_tunnel_create(int fd, int version, u32 tunnel_id,
+		       u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg,
+		       struct l2tp_tunnel **tunnelp);
+int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
+			 struct l2tp_tunnel_cfg *cfg);
+void 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);
+int l2tp_session_register(struct l2tp_session *session,
+			  struct l2tp_tunnel *tunnel);
+void l2tp_session_delete(struct l2tp_session *session);
+
+/* Receive path helpers.  If data sequencing is enabled for the session these
+ * functions handle queuing and reordering prior to passing packets to the
+ * pseudowire code to be passed to userspace.
+ */
+void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
+		      unsigned char *ptr, unsigned char *optr, u16 hdrflags,
+		      int length);
+int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb);
+
+/* Transmit path helpers for sending packets over the tunnel socket. */
+void l2tp_session_set_header_len(struct l2tp_session *session, int version);
+int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb);
+
+/* Pseudowire management.
+ * Pseudowires should register with l2tp core on module init, and unregister
+ * on module exit.
+ */
+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);
+
+/* IOCTL helper for IP encap modules. */
+int l2tp_ioctl(struct sock *sk, int cmd, unsigned long arg);
+
+/* Extract the tunnel structure from a socket's sk_user_data pointer,
+ * validating the tunnel magic feather.
+ */
+struct l2tp_tunnel *l2tp_sk_to_tunnel(struct sock *sk);
+
+static inline int l2tp_get_l2specific_len(struct l2tp_session *session)
+{
+	switch (session->l2specific_type) {
+	case L2TP_L2SPECTYPE_DEFAULT:
+		return 4;
+	case L2TP_L2SPECTYPE_NONE:
+	default:
+		return 0;
+	}
+}
+
+static inline u32 l2tp_tunnel_dst_mtu(const struct l2tp_tunnel *tunnel)
+{
+	struct dst_entry *dst;
+	u32 mtu;
+
+	dst = sk_dst_get(tunnel->sock);
+	if (!dst)
+		return 0;
+
+	mtu = dst_mtu(dst);
+	dst_release(dst);
+
+	return mtu;
+}
+
+#ifdef CONFIG_XFRM
+static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
+{
+	struct sock *sk = tunnel->sock;
+
+	return sk && (rcu_access_pointer(sk->sk_policy[0]) ||
+		      rcu_access_pointer(sk->sk_policy[1]));
+}
+#else
+static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
+{
+	return false;
+}
+#endif
+
+static inline int l2tp_v3_ensure_opt_in_linear(struct l2tp_session *session, struct sk_buff *skb,
+					       unsigned char **ptr, unsigned char **optr)
+{
+	int opt_len = session->peer_cookie_len + l2tp_get_l2specific_len(session);
+
+	if (opt_len > 0) {
+		int off = *ptr - *optr;
+
+		if (!pskb_may_pull(skb, off + opt_len))
+			return -1;
+
+		if (skb->data != *optr) {
+			*optr = skb->data;
+			*ptr = skb->data + off;
+		}
+	}
+
+	return 0;
+}
+
+#define MODULE_ALIAS_L2TP_PWTYPE(type) \
+	MODULE_ALIAS("net-l2tp-type-" __stringify(type))
+
+#endif /* _L2TP_CORE_H_ */
diff --git a/net/l2tp/l2tp_debugfs.c b/net/l2tp/l2tp_debugfs.c
new file mode 100644
index 000000000..4595b56d1
--- /dev/null
+++ b/net/l2tp/l2tp_debugfs.c
@@ -0,0 +1,348 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* L2TP subsystem debugfs
+ *
+ * Copyright (c) 2010 Katalix Systems Ltd
+ */
+
+#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;
+
+struct l2tp_dfs_seq_data {
+	struct net	*net;
+	netns_tracker	ns_tracker;
+	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)
+{
+	/* Drop reference taken during previous invocation */
+	if (pd->tunnel)
+		l2tp_tunnel_dec_refcount(pd->tunnel);
+
+	pd->tunnel = l2tp_tunnel_get_nth(pd->net, pd->tunnel_idx);
+	pd->tunnel_idx++;
+}
+
+static void l2tp_dfs_next_session(struct l2tp_dfs_seq_data *pd)
+{
+	/* Drop reference taken during previous invocation */
+	if (pd->session)
+		l2tp_session_dec_refcount(pd->session);
+
+	pd->session = l2tp_session_get_nth(pd->tunnel, pd->session_idx);
+	pd->session_idx++;
+
+	if (!pd->session) {
+		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;
+
+	if (WARN_ON(!m->private)) {
+		pd = NULL;
+		goto out;
+	}
+	pd = m->private;
+
+	if (!pd->tunnel)
+		l2tp_dfs_next_tunnel(pd);
+	else
+		l2tp_dfs_next_session(pd);
+
+	/* NULL tunnel and session indicates end of list */
+	if (!pd->tunnel && !pd->session)
+		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)
+{
+	struct l2tp_dfs_seq_data *pd = v;
+
+	if (!pd || pd == SEQ_START_TOKEN)
+		return;
+
+	/* Drop reference taken by last invocation of l2tp_dfs_next_session()
+	 * or l2tp_dfs_next_tunnel().
+	 */
+	if (pd->session) {
+		l2tp_session_dec_refcount(pd->session);
+		pd->session = NULL;
+	}
+	if (pd->tunnel) {
+		l2tp_tunnel_dec_refcount(pd->tunnel);
+		pd->tunnel = NULL;
+	}
+}
+
+static void l2tp_dfs_seq_tunnel_show(struct seq_file *m, void *v)
+{
+	struct l2tp_tunnel *tunnel = v;
+	struct l2tp_session *session;
+	int session_count = 0;
+	int hash;
+
+	rcu_read_lock_bh();
+	for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
+		hlist_for_each_entry_rcu(session, &tunnel->session_hlist[hash], hlist) {
+			/* Session ID of zero is a dummy/reserved value used by pppol2tp */
+			if (session->session_id == 0)
+				continue;
+
+			session_count++;
+		}
+	}
+	rcu_read_unlock_bh();
+
+	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);
+		}
+#endif
+		if (tunnel->sock->sk_family == AF_INET)
+			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 ? refcount_read(&tunnel->sock->sk_refcnt) : 0,
+		   refcount_read(&tunnel->ref_count));
+	seq_printf(m, " %08x rx %ld/%ld/%ld rx %ld/%ld/%ld\n",
+		   0,
+		   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 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 %u, ns %u\n", session->nr, session->ns);
+	seq_printf(m, "   refcnt %d\n", refcount_read(&session->ref_count));
+	seq_printf(m, "   config 0/0/%c/%c/-/%s %08x %u\n",
+		   session->recv_seq ? 'R' : '-',
+		   session->send_seq ? 'S' : '-',
+		   session->lns_mode ? "LNS" : "LAC",
+		   0,
+		   jiffies_to_msecs(session->reorder_timeout));
+	seq_printf(m, "   offset 0 l2specific %hu/%d\n",
+		   session->l2specific_type, l2tp_get_l2specific_len(session));
+	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_puts(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_puts(m, "\n");
+	}
+
+	seq_printf(m, "   %u/%u 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)
+		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;
+	}
+
+	if (!pd->session)
+		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)
+		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;
+	}
+	netns_tracker_alloc(pd->net, &pd->ns_tracker, GFP_KERNEL);
+	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_track(pd->net, &pd->ns_tracker);
+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_track(pd->net, &pd->ns_tracker);
+	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)
+{
+	rootdir = debugfs_create_dir("l2tp", NULL);
+
+	debugfs_create_file("tunnels", 0600, rootdir, NULL, &l2tp_dfs_fops);
+
+	pr_info("L2TP debugfs support\n");
+
+	return 0;
+}
+
+static void __exit l2tp_debugfs_exit(void)
+{
+	debugfs_remove_recursive(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..f2ae03c40
--- /dev/null
+++ b/net/l2tp/l2tp_eth.c
@@ -0,0 +1,370 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* L2TPv3 ethernet pseudowire driver
+ *
+ * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
+ */
+
+#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 <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/udp.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 l2tp_session	*session;
+	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 __rcu *dev;
+};
+
+static int l2tp_eth_dev_init(struct net_device *dev)
+{
+	eth_hw_addr_random(dev);
+	eth_broadcast_addr(dev->broadcast);
+	netdev_lockdep_set_classes(dev);
+
+	return 0;
+}
+
+static void l2tp_eth_dev_uninit(struct net_device *dev)
+{
+	struct l2tp_eth *priv = netdev_priv(dev);
+	struct l2tp_eth_sess *spriv;
+
+	spriv = l2tp_session_priv(priv->session);
+	RCU_INIT_POINTER(spriv->dev, NULL);
+	/* No need for synchronize_net() here. We're called by
+	 * unregister_netdev*(), which does the synchronisation for us.
+	 */
+}
+
+static netdev_tx_t 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);
+
+	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 void l2tp_eth_get_stats64(struct net_device *dev,
+				 struct rtnl_link_stats64 *stats)
+{
+	struct l2tp_eth *priv = netdev_priv(dev);
+
+	stats->tx_bytes   = (unsigned long)atomic_long_read(&priv->tx_bytes);
+	stats->tx_packets = (unsigned long)atomic_long_read(&priv->tx_packets);
+	stats->tx_dropped = (unsigned long)atomic_long_read(&priv->tx_dropped);
+	stats->rx_bytes   = (unsigned long)atomic_long_read(&priv->rx_bytes);
+	stats->rx_packets = (unsigned long)atomic_long_read(&priv->rx_packets);
+	stats->rx_errors  = (unsigned long)atomic_long_read(&priv->rx_errors);
+}
+
+static const 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 struct device_type l2tpeth_type = {
+	.name = "l2tpeth",
+};
+
+static void l2tp_eth_dev_setup(struct net_device *dev)
+{
+	SET_NETDEV_DEVTYPE(dev, &l2tpeth_type);
+	ether_setup(dev);
+	dev->priv_flags		&= ~IFF_TX_SKB_SHARING;
+	dev->features		|= NETIF_F_LLTX;
+	dev->netdev_ops		= &l2tp_eth_netdev_ops;
+	dev->needs_free_netdev	= true;
+}
+
+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;
+	struct l2tp_eth *priv;
+
+	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_ct(skb);
+
+	rcu_read_lock();
+	dev = rcu_dereference(spriv->dev);
+	if (!dev)
+		goto error_rcu;
+
+	priv = netdev_priv(dev);
+	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);
+	}
+	rcu_read_unlock();
+
+	return;
+
+error_rcu:
+	rcu_read_unlock();
+error:
+	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);
+
+		rtnl_lock();
+		dev = rtnl_dereference(spriv->dev);
+		if (dev) {
+			unregister_netdevice(dev);
+			rtnl_unlock();
+			module_put(THIS_MODULE);
+		} else {
+			rtnl_unlock();
+		}
+	}
+}
+
+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;
+
+	rcu_read_lock();
+	dev = rcu_dereference(spriv->dev);
+	if (!dev) {
+		rcu_read_unlock();
+		return;
+	}
+	dev_hold(dev);
+	rcu_read_unlock();
+
+	seq_printf(m, "   interface %s\n", dev->name);
+
+	dev_put(dev);
+}
+
+static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
+				struct l2tp_session *session,
+				struct net_device *dev)
+{
+	unsigned int overhead = 0;
+	u32 l3_overhead = 0;
+	u32 mtu;
+
+	/* if the encap is UDP, account for UDP header size */
+	if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
+		overhead += sizeof(struct udphdr);
+		dev->needed_headroom += sizeof(struct udphdr);
+	}
+
+	lock_sock(tunnel->sock);
+	l3_overhead = kernel_sock_ip_overhead(tunnel->sock);
+	release_sock(tunnel->sock);
+
+	if (l3_overhead == 0) {
+		/* L3 Overhead couldn't be identified, this could be
+		 * because tunnel->sock was NULL or the socket's
+		 * address family was not IPv4 or IPv6,
+		 * dev mtu stays at 1500.
+		 */
+		return;
+	}
+	/* Adjust MTU, factor overhead - underlay L3, overlay L2 hdr
+	 * UDP overhead, if any, was already factored in above.
+	 */
+	overhead += session->hdr_len + ETH_HLEN + l3_overhead;
+
+	mtu = l2tp_tunnel_dst_mtu(tunnel) - overhead;
+	if (mtu < dev->min_mtu || mtu > dev->max_mtu)
+		dev->mtu = ETH_DATA_LEN - overhead;
+	else
+		dev->mtu = mtu;
+
+	dev->needed_headroom += session->hdr_len;
+}
+
+static int l2tp_eth_create(struct net *net, struct l2tp_tunnel *tunnel,
+			   u32 session_id, u32 peer_session_id,
+			   struct l2tp_session_cfg *cfg)
+{
+	unsigned char name_assign_type;
+	struct net_device *dev;
+	char name[IFNAMSIZ];
+	struct l2tp_session *session;
+	struct l2tp_eth *priv;
+	struct l2tp_eth_sess *spriv;
+	int rc;
+
+	if (cfg->ifname) {
+		strscpy(name, cfg->ifname, IFNAMSIZ);
+		name_assign_type = NET_NAME_USER;
+	} else {
+		strcpy(name, L2TP_ETH_DEV_NAME);
+		name_assign_type = NET_NAME_ENUM;
+	}
+
+	session = l2tp_session_create(sizeof(*spriv), tunnel, session_id,
+				      peer_session_id, cfg);
+	if (IS_ERR(session)) {
+		rc = PTR_ERR(session);
+		goto err;
+	}
+
+	dev = alloc_netdev(sizeof(*priv), name, name_assign_type,
+			   l2tp_eth_dev_setup);
+	if (!dev) {
+		rc = -ENOMEM;
+		goto err_sess;
+	}
+
+	dev_net_set(dev, net);
+	dev->min_mtu = 0;
+	dev->max_mtu = ETH_MAX_MTU;
+	l2tp_eth_adjust_mtu(tunnel, session, dev);
+
+	priv = netdev_priv(dev);
+	priv->session = session;
+
+	session->recv_skb = l2tp_eth_dev_recv;
+	session->session_close = l2tp_eth_delete;
+	if (IS_ENABLED(CONFIG_L2TP_DEBUGFS))
+		session->show = l2tp_eth_show;
+
+	spriv = l2tp_session_priv(session);
+
+	l2tp_session_inc_refcount(session);
+
+	rtnl_lock();
+
+	/* Register both device and session while holding the rtnl lock. This
+	 * ensures that l2tp_eth_delete() will see that there's a device to
+	 * unregister, even if it happened to run before we assign spriv->dev.
+	 */
+	rc = l2tp_session_register(session, tunnel);
+	if (rc < 0) {
+		rtnl_unlock();
+		goto err_sess_dev;
+	}
+
+	rc = register_netdevice(dev);
+	if (rc < 0) {
+		rtnl_unlock();
+		l2tp_session_delete(session);
+		l2tp_session_dec_refcount(session);
+		free_netdev(dev);
+
+		return rc;
+	}
+
+	strscpy(session->ifname, dev->name, IFNAMSIZ);
+	rcu_assign_pointer(spriv->dev, dev);
+
+	rtnl_unlock();
+
+	l2tp_session_dec_refcount(session);
+
+	__module_get(THIS_MODULE);
+
+	return 0;
+
+err_sess_dev:
+	l2tp_session_dec_refcount(session);
+	free_netdev(dev);
+err_sess:
+	kfree(session);
+err:
+	return rc;
+}
+
+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 err;
+
+	pr_info("L2TP ethernet pseudowire support (L2TPv3)\n");
+
+	return 0;
+
+err:
+	return err;
+}
+
+static void __exit l2tp_eth_exit(void)
+{
+	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");
+MODULE_ALIAS_L2TP_PWTYPE(5);
diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
new file mode 100644
index 000000000..41a74fc84
--- /dev/null
+++ b/net/l2tp/l2tp_ip.c
@@ -0,0 +1,684 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* L2TPv3 IP encapsulation support
+ *
+ * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <asm/ioctls.h>
+#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/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(const struct net *net, __be32 laddr,
+					  __be32 raddr, int dif, u32 tunnel_id)
+{
+	struct sock *sk;
+
+	sk_for_each_bound(sk, &l2tp_ip_bind_table) {
+		const struct l2tp_ip_sock *l2tp = l2tp_ip_sk(sk);
+		const struct inet_sock *inet = inet_sk(sk);
+		int bound_dev_if;
+
+		if (!net_eq(sock_net(sk), net))
+			continue;
+
+		bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
+		if (bound_dev_if && dif && bound_dev_if != dif)
+			continue;
+
+		if (inet->inet_rcv_saddr && laddr &&
+		    inet->inet_rcv_saddr != laddr)
+			continue;
+
+		if (inet->inet_daddr && raddr && inet->inet_daddr != raddr)
+			continue;
+
+		if (l2tp->conn_id != tunnel_id)
+			continue;
+
+		goto found;
+	}
+
+	sk = NULL;
+found:
+	return sk;
+}
+
+/* When processing receive frames, there are two cases to
+ * consider. Data frames consist of a non-zero session-id and an
+ * optional cookie. Control frames consist of a regular L2TP header
+ * preceded by 32-bits of zeros.
+ *
+ * L2TPv3 Session Header Over IP
+ *
+ *  0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                           Session ID                          |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |               Cookie (optional, maximum 64 bits)...
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *                                                                 |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * L2TPv3 Control Message Header Over IP
+ *
+ *  0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                      (32 bits of zeros)                       |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |T|L|x|x|S|x|x|x|x|x|x|x|  Ver  |             Length            |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                     Control Connection ID                     |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |               Ns              |               Nr              |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * All control frames are passed to userspace.
+ */
+static int l2tp_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;
+	struct iphdr *iph;
+
+	if (!pskb_may_pull(skb, 4))
+		goto discard;
+
+	/* Point to L2TP header */
+	optr = skb->data;
+	ptr = skb->data;
+	session_id = ntohl(*((__be32 *)ptr));
+	ptr += 4;
+
+	/* RFC3931: L2TP/IP packets have the first 4 bytes containing
+	 * the session_id. If it is 0, the packet is a L2TP control
+	 * frame and the session_id value can be discarded.
+	 */
+	if (session_id == 0) {
+		__skb_pull(skb, 4);
+		goto pass_up;
+	}
+
+	/* Ok, this is a data packet. Lookup the session. */
+	session = l2tp_session_get(net, session_id);
+	if (!session)
+		goto discard;
+
+	tunnel = session->tunnel;
+	if (!tunnel)
+		goto discard_sess;
+
+	if (l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
+		goto discard_sess;
+
+	l2tp_recv_common(session, skb, ptr, optr, 0, skb->len);
+	l2tp_session_dec_refcount(session);
+
+	return 0;
+
+pass_up:
+	/* Get the tunnel_id from the L2TP header */
+	if (!pskb_may_pull(skb, 12))
+		goto discard;
+
+	if ((skb->data[0] & 0xc0) != 0xc0)
+		goto discard;
+
+	tunnel_id = ntohl(*(__be32 *)&skb->data[4]);
+	iph = (struct iphdr *)skb_network_header(skb);
+
+	read_lock_bh(&l2tp_ip_lock);
+	sk = __l2tp_ip_bind_lookup(net, iph->daddr, iph->saddr, inet_iif(skb),
+				   tunnel_id);
+	if (!sk) {
+		read_unlock_bh(&l2tp_ip_lock);
+		goto discard;
+	}
+	sock_hold(sk);
+	read_unlock_bh(&l2tp_ip_lock);
+
+	if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
+		goto discard_put;
+
+	nf_reset_ct(skb);
+
+	return sk_receive_skb(sk, skb, 1);
+
+discard_sess:
+	l2tp_session_dec_refcount(session);
+	goto discard;
+
+discard_put:
+	sock_put(sk);
+
+discard:
+	kfree_skb(skb);
+	return 0;
+}
+
+static int l2tp_ip_hash(struct sock *sk)
+{
+	if (sk_unhashed(sk)) {
+		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_unhash(struct sock *sk)
+{
+	if (sk_unhashed(sk))
+		return;
+	write_lock_bh(&l2tp_ip_lock);
+	sk_del_node_init(sk);
+	write_unlock_bh(&l2tp_ip_lock);
+}
+
+static int l2tp_ip_open(struct sock *sk)
+{
+	/* Prevent autobind. We don't have ports. */
+	inet_sk(sk)->inet_num = IPPROTO_L2TP;
+
+	l2tp_ip_hash(sk);
+	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 l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
+	struct sk_buff *skb;
+
+	while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
+		kfree_skb(skb);
+
+	if (tunnel)
+		l2tp_tunnel_delete(tunnel);
+}
+
+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 (addr_len < sizeof(struct sockaddr_l2tpip))
+		return -EINVAL;
+	if (addr->l2tp_family != AF_INET)
+		return -EINVAL;
+
+	lock_sock(sk);
+
+	ret = -EINVAL;
+	if (!sock_flag(sk, SOCK_ZAPPED))
+		goto out;
+
+	if (sk->sk_state != TCP_CLOSE)
+		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 = addr->l2tp_addr.s_addr;
+		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 */
+
+	write_lock_bh(&l2tp_ip_lock);
+	if (__l2tp_ip_bind_lookup(net, addr->l2tp_addr.s_addr, 0,
+				  sk->sk_bound_dev_if, addr->l2tp_conn_id)) {
+		write_unlock_bh(&l2tp_ip_lock);
+		ret = -EADDRINUSE;
+		goto out;
+	}
+
+	sk_dst_reset(sk);
+	l2tp_ip_sk(sk)->conn_id = addr->l2tp_conn_id;
+
+	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;
+}
+
+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 (addr_len < sizeof(*lsa))
+		return -EINVAL;
+
+	if (ipv4_is_multicast(lsa->l2tp_addr.s_addr))
+		return -EINVAL;
+
+	lock_sock(sk);
+
+	/* Must bind first - autobinding does not work */
+	if (sock_flag(sk, SOCK_ZAPPED)) {
+		rc = -EINVAL;
+		goto out_sk;
+	}
+
+	rc = __ip4_datagram_connect(sk, uaddr, addr_len);
+	if (rc < 0)
+		goto out_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);
+
+out_sk:
+	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 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;
+	}
+	return sizeof(*lsa);
+}
+
+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 0;
+}
+
+/* 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) {
+		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 don't 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 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, &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;
+}
+
+int l2tp_ioctl(struct sock *sk, int cmd, unsigned long arg)
+{
+	struct sk_buff *skb;
+	int amount;
+
+	switch (cmd) {
+	case SIOCOUTQ:
+		amount = sk_wmem_alloc_get(sk);
+		break;
+	case SIOCINQ:
+		spin_lock_bh(&sk->sk_receive_queue.lock);
+		skb = skb_peek(&sk->sk_receive_queue);
+		amount = skb ? skb->len : 0;
+		spin_unlock_bh(&sk->sk_receive_queue.lock);
+		break;
+
+	default:
+		return -ENOIOCTLCMD;
+	}
+
+	return put_user(amount, (int __user *)arg);
+}
+EXPORT_SYMBOL_GPL(l2tp_ioctl);
+
+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		   = l2tp_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		   = l2tp_ip_hash,
+	.unhash		   = l2tp_ip_unhash,
+	.obj_size	   = sizeof(struct l2tp_ip_sock),
+};
+
+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,
+	.gettstamp	   = sock_gettstamp,
+	.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,
+};
+
+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,
+};
+
+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 values of SOCK_DGRAM (2) as type and IPPROTO_L2TP (115) as protocol,
+ * because __stringify doesn't like enums
+ */
+MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 115, 2);
+MODULE_ALIAS_NET_PF_PROTO(PF_INET, 115);
diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
new file mode 100644
index 000000000..314ec3a51
--- /dev/null
+++ b/net/l2tp/l2tp_ip6.c
@@ -0,0 +1,813 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* L2TPv3 IP encapsulation support for IPv6
+ *
+ * Copyright (c) 2012 Katalix Systems Ltd
+ */
+
+#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/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(const struct net *net,
+					   const struct in6_addr *laddr,
+					   const struct in6_addr *raddr,
+					   int dif, u32 tunnel_id)
+{
+	struct sock *sk;
+
+	sk_for_each_bound(sk, &l2tp_ip6_bind_table) {
+		const struct in6_addr *sk_laddr = inet6_rcv_saddr(sk);
+		const struct in6_addr *sk_raddr = &sk->sk_v6_daddr;
+		const struct l2tp_ip6_sock *l2tp = l2tp_ip6_sk(sk);
+		int bound_dev_if;
+
+		if (!net_eq(sock_net(sk), net))
+			continue;
+
+		bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
+		if (bound_dev_if && dif && bound_dev_if != dif)
+			continue;
+
+		if (sk_laddr && !ipv6_addr_any(sk_laddr) &&
+		    !ipv6_addr_any(laddr) && !ipv6_addr_equal(sk_laddr, laddr))
+			continue;
+
+		if (!ipv6_addr_any(sk_raddr) && raddr &&
+		    !ipv6_addr_any(raddr) && !ipv6_addr_equal(sk_raddr, raddr))
+			continue;
+
+		if (l2tp->conn_id != tunnel_id)
+			continue;
+
+		goto found;
+	}
+
+	sk = NULL;
+found:
+	return sk;
+}
+
+/* When processing receive frames, there are two cases to
+ * consider. Data frames consist of a non-zero session-id and an
+ * optional cookie. Control frames consist of a regular L2TP header
+ * preceded by 32-bits of zeros.
+ *
+ * L2TPv3 Session Header Over IP
+ *
+ *  0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                           Session ID                          |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |               Cookie (optional, maximum 64 bits)...
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *                                                                 |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * L2TPv3 Control Message Header Over IP
+ *
+ *  0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                      (32 bits of zeros)                       |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |T|L|x|x|S|x|x|x|x|x|x|x|  Ver  |             Length            |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                     Control Connection ID                     |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |               Ns              |               Nr              |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * All control frames are passed to userspace.
+ */
+static int l2tp_ip6_recv(struct sk_buff *skb)
+{
+	struct net *net = dev_net(skb->dev);
+	struct sock *sk;
+	u32 session_id;
+	u32 tunnel_id;
+	unsigned char *ptr, *optr;
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel = NULL;
+	struct ipv6hdr *iph;
+
+	if (!pskb_may_pull(skb, 4))
+		goto discard;
+
+	/* Point to L2TP header */
+	optr = skb->data;
+	ptr = skb->data;
+	session_id = ntohl(*((__be32 *)ptr));
+	ptr += 4;
+
+	/* RFC3931: L2TP/IP packets have the first 4 bytes containing
+	 * the session_id. If it is 0, the packet is a L2TP control
+	 * frame and the session_id value can be discarded.
+	 */
+	if (session_id == 0) {
+		__skb_pull(skb, 4);
+		goto pass_up;
+	}
+
+	/* Ok, this is a data packet. Lookup the session. */
+	session = l2tp_session_get(net, session_id);
+	if (!session)
+		goto discard;
+
+	tunnel = session->tunnel;
+	if (!tunnel)
+		goto discard_sess;
+
+	if (l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
+		goto discard_sess;
+
+	l2tp_recv_common(session, skb, ptr, optr, 0, skb->len);
+	l2tp_session_dec_refcount(session);
+
+	return 0;
+
+pass_up:
+	/* Get the tunnel_id from the L2TP header */
+	if (!pskb_may_pull(skb, 12))
+		goto discard;
+
+	if ((skb->data[0] & 0xc0) != 0xc0)
+		goto discard;
+
+	tunnel_id = ntohl(*(__be32 *)&skb->data[4]);
+	iph = ipv6_hdr(skb);
+
+	read_lock_bh(&l2tp_ip6_lock);
+	sk = __l2tp_ip6_bind_lookup(net, &iph->daddr, &iph->saddr,
+				    inet6_iif(skb), tunnel_id);
+	if (!sk) {
+		read_unlock_bh(&l2tp_ip6_lock);
+		goto discard;
+	}
+	sock_hold(sk);
+	read_unlock_bh(&l2tp_ip6_lock);
+
+	if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
+		goto discard_put;
+
+	nf_reset_ct(skb);
+
+	return sk_receive_skb(sk, skb, 1);
+
+discard_sess:
+	l2tp_session_dec_refcount(session);
+	goto discard;
+
+discard_put:
+	sock_put(sk);
+
+discard:
+	kfree_skb(skb);
+	return 0;
+}
+
+static int l2tp_ip6_hash(struct sock *sk)
+{
+	if (sk_unhashed(sk)) {
+		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_unhash(struct sock *sk)
+{
+	if (sk_unhashed(sk))
+		return;
+	write_lock_bh(&l2tp_ip6_lock);
+	sk_del_node_init(sk);
+	write_unlock_bh(&l2tp_ip6_lock);
+}
+
+static int l2tp_ip6_open(struct sock *sk)
+{
+	/* Prevent autobind. We don't have ports. */
+	inet_sk(sk)->inet_num = IPPROTO_L2TP;
+
+	l2tp_ip6_hash(sk);
+	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_sk_to_tunnel(sk);
+
+	lock_sock(sk);
+	ip6_flush_pending_frames(sk);
+	release_sock(sk);
+
+	if (tunnel)
+		l2tp_tunnel_delete(tunnel);
+}
+
+static int l2tp_ip6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct ipv6_pinfo *np = inet6_sk(sk);
+	struct sockaddr_l2tpip6 *addr = (struct sockaddr_l2tpip6 *)uaddr;
+	struct net *net = sock_net(sk);
+	__be32 v4addr = 0;
+	int bound_dev_if;
+	int addr_type;
+	int err;
+
+	if (addr->l2tp_family != AF_INET6)
+		return -EINVAL;
+	if (addr_len < sizeof(*addr))
+		return -EINVAL;
+
+	addr_type = ipv6_addr_type(&addr->l2tp_addr);
+
+	/* l2tp_ip6 sockets are IPv6 only */
+	if (addr_type == IPV6_ADDR_MAPPED)
+		return -EADDRNOTAVAIL;
+
+	/* L2TP is point-point, not multicast */
+	if (addr_type & IPV6_ADDR_MULTICAST)
+		return -EADDRNOTAVAIL;
+
+	lock_sock(sk);
+
+	err = -EINVAL;
+	if (!sock_flag(sk, SOCK_ZAPPED))
+		goto out_unlock;
+
+	if (sk->sk_state != TCP_CLOSE)
+		goto out_unlock;
+
+	bound_dev_if = sk->sk_bound_dev_if;
+
+	/* Check if the address belongs to the host. */
+	rcu_read_lock();
+	if (addr_type != IPV6_ADDR_ANY) {
+		struct net_device *dev = NULL;
+
+		if (addr_type & IPV6_ADDR_LINKLOCAL) {
+			if (addr->l2tp_scope_id)
+				bound_dev_if = addr->l2tp_scope_id;
+
+			/* Binding to link-local address requires an
+			 * interface.
+			 */
+			if (!bound_dev_if)
+				goto out_unlock_rcu;
+
+			err = -ENODEV;
+			dev = dev_get_by_index_rcu(sock_net(sk), bound_dev_if);
+			if (!dev)
+				goto out_unlock_rcu;
+		}
+
+		/* ipv4 addr of the socket is invalid.  Only the
+		 * unspecified and mapped address have a v4 equivalent.
+		 */
+		v4addr = LOOPBACK4_IPV6;
+		err = -EADDRNOTAVAIL;
+		if (!ipv6_chk_addr(sock_net(sk), &addr->l2tp_addr, dev, 0))
+			goto out_unlock_rcu;
+	}
+	rcu_read_unlock();
+
+	write_lock_bh(&l2tp_ip6_lock);
+	if (__l2tp_ip6_bind_lookup(net, &addr->l2tp_addr, NULL, bound_dev_if,
+				   addr->l2tp_conn_id)) {
+		write_unlock_bh(&l2tp_ip6_lock);
+		err = -EADDRINUSE;
+		goto out_unlock;
+	}
+
+	inet->inet_saddr = v4addr;
+	inet->inet_rcv_saddr = v4addr;
+	sk->sk_bound_dev_if = bound_dev_if;
+	sk->sk_v6_rcv_saddr = addr->l2tp_addr;
+	np->saddr = addr->l2tp_addr;
+
+	l2tp_ip6_sk(sk)->conn_id = addr->l2tp_conn_id;
+
+	sk_add_bind_node(sk, &l2tp_ip6_bind_table);
+	sk_del_node_init(sk);
+	write_unlock_bh(&l2tp_ip6_lock);
+
+	sock_reset_flag(sk, SOCK_ZAPPED);
+	release_sock(sk);
+	return 0;
+
+out_unlock_rcu:
+	rcu_read_unlock();
+out_unlock:
+	release_sock(sk);
+
+	return err;
+}
+
+static int l2tp_ip6_connect(struct sock *sk, struct sockaddr *uaddr,
+			    int addr_len)
+{
+	struct sockaddr_l2tpip6 *lsa = (struct sockaddr_l2tpip6 *)uaddr;
+	struct sockaddr_in6	*usin = (struct sockaddr_in6 *)uaddr;
+	struct in6_addr	*daddr;
+	int	addr_type;
+	int rc;
+
+	if (addr_len < sizeof(*lsa))
+		return -EINVAL;
+
+	if (usin->sin6_family != AF_INET6)
+		return -EINVAL;
+
+	addr_type = ipv6_addr_type(&usin->sin6_addr);
+	if (addr_type & IPV6_ADDR_MULTICAST)
+		return -EINVAL;
+
+	if (addr_type & IPV6_ADDR_MAPPED) {
+		daddr = &usin->sin6_addr;
+		if (ipv4_is_multicast(daddr->s6_addr32[3]))
+			return -EINVAL;
+	}
+
+	lock_sock(sk);
+
+	 /* Must bind first - autobinding does not work */
+	if (sock_flag(sk, SOCK_ZAPPED)) {
+		rc = -EINVAL;
+		goto out_sk;
+	}
+
+	rc = __ip6_datagram_connect(sk, uaddr, addr_len);
+	if (rc < 0)
+		goto out_sk;
+
+	l2tp_ip6_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;
+
+	write_lock_bh(&l2tp_ip6_lock);
+	hlist_del_init(&sk->sk_bind_node);
+	sk_add_bind_node(sk, &l2tp_ip6_bind_table);
+	write_unlock_bh(&l2tp_ip6_lock);
+
+out_sk:
+	release_sock(sk);
+
+	return rc;
+}
+
+static int l2tp_ip6_disconnect(struct sock *sk, int flags)
+{
+	if (sock_flag(sk, SOCK_ZAPPED))
+		return 0;
+
+	return __udp_disconnect(sk, flags);
+}
+
+static int l2tp_ip6_getname(struct socket *sock, struct sockaddr *uaddr,
+			    int 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 = READ_ONCE(sk->sk_bound_dev_if);
+	return sizeof(*lsa);
+}
+
+static int l2tp_ip6_backlog_recv(struct sock *sk, struct sk_buff *skb)
+{
+	int rc;
+
+	/* Charge it to the socket, dropping if the queue is full. */
+	rc = sock_queue_rcv_skb(sk, skb);
+	if (rc < 0)
+		goto drop;
+
+	return 0;
+
+drop:
+	IP_INC_STATS(sock_net(sk), IPSTATS_MIB_INDISCARDS);
+	kfree_skb(skb);
+	return -1;
+}
+
+static int l2tp_ip6_push_pending_frames(struct sock *sk)
+{
+	struct sk_buff *skb;
+	__be32 *transhdr = NULL;
+	int err = 0;
+
+	skb = skb_peek(&sk->sk_write_queue);
+	if (!skb)
+		goto out;
+
+	transhdr = (__be32 *)skb_transport_header(skb);
+	*transhdr = 0;
+
+	err = ip6_push_pending_frames(sk);
+
+out:
+	return err;
+}
+
+/* Userspace will call sendmsg() on the tunnel socket to send L2TP
+ * control frames.
+ */
+static int l2tp_ip6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
+{
+	struct ipv6_txoptions opt_space;
+	DECLARE_SOCKADDR(struct sockaddr_l2tpip6 *, lsa, msg->msg_name);
+	struct in6_addr *daddr, *final_p, final;
+	struct ipv6_pinfo *np = inet6_sk(sk);
+	struct ipv6_txoptions *opt_to_free = NULL;
+	struct ipv6_txoptions *opt = NULL;
+	struct ip6_flowlabel *flowlabel = NULL;
+	struct dst_entry *dst = NULL;
+	struct flowi6 fl6;
+	struct ipcm6_cookie ipc6;
+	int addr_len = msg->msg_namelen;
+	int transhdrlen = 4; /* zero session-id */
+	int ulen;
+	int err;
+
+	/* Rough check on arithmetic overflow,
+	 * better check is made in ip6_append_data().
+	 */
+	if (len > INT_MAX - transhdrlen)
+		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 = READ_ONCE(sk->sk_mark);
+	fl6.flowi6_uid = sk->sk_uid;
+
+	ipcm6_init(&ipc6);
+
+	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 (IS_ERR(flowlabel))
+					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 = READ_ONCE(sk->sk_bound_dev_if);
+
+	if (msg->msg_controllen) {
+		opt = &opt_space;
+		memset(opt, 0, sizeof(struct ipv6_txoptions));
+		opt->tot_len = sizeof(struct ipv6_txoptions);
+		ipc6.opt = opt;
+
+		err = ip6_datagram_send_ctl(sock_net(sk), sk, msg, &fl6, &ipc6);
+		if (err < 0) {
+			fl6_sock_release(flowlabel);
+			return err;
+		}
+		if ((fl6.flowlabel & IPV6_FLOWLABEL_MASK) && !flowlabel) {
+			flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
+			if (IS_ERR(flowlabel))
+				return -EINVAL;
+		}
+		if (!(opt->opt_nflen | opt->opt_flen))
+			opt = NULL;
+	}
+
+	if (!opt) {
+		opt = txopt_get(np);
+		opt_to_free = opt;
+	}
+	if (flowlabel)
+		opt = fl6_merge_options(&opt_space, flowlabel, opt);
+	opt = ipv6_fixup_options(&opt_space, opt);
+	ipc6.opt = opt;
+
+	fl6.flowi6_proto = sk->sk_protocol;
+	if (!ipv6_addr_any(daddr))
+		fl6.daddr = *daddr;
+	else
+		fl6.daddr.s6_addr[15] = 0x1; /* :: means loopback (BSD'ism) */
+	if (ipv6_addr_any(&fl6.saddr) && !ipv6_addr_any(&np->saddr))
+		fl6.saddr = np->saddr;
+
+	final_p = fl6_update_dst(&fl6, opt, &final);
+
+	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
+		fl6.flowi6_oif = np->mcast_oif;
+	else if (!fl6.flowi6_oif)
+		fl6.flowi6_oif = np->ucast_oif;
+
+	security_sk_classify_flow(sk, flowi6_to_flowi_common(&fl6));
+
+	if (ipc6.tclass < 0)
+		ipc6.tclass = np->tclass;
+
+	fl6.flowlabel = ip6_make_flowinfo(ipc6.tclass, fl6.flowlabel);
+
+	dst = ip6_dst_lookup_flow(sock_net(sk), sk, &fl6, final_p);
+	if (IS_ERR(dst)) {
+		err = PTR_ERR(dst);
+		goto out;
+	}
+
+	if (ipc6.hlimit < 0)
+		ipc6.hlimit = ip6_sk_dst_hoplimit(np, &fl6, dst);
+
+	if (ipc6.dontfrag < 0)
+		ipc6.dontfrag = np->dontfrag;
+
+	if (msg->msg_flags & MSG_CONFIRM)
+		goto do_confirm;
+
+back_from_confirm:
+	lock_sock(sk);
+	ulen = len + skb_queue_empty(&sk->sk_write_queue) ? transhdrlen : 0;
+	err = ip6_append_data(sk, ip_generic_getfrag, msg,
+			      ulen, transhdrlen, &ipc6,
+			      &fl6, (struct rt6_info *)dst,
+			      msg->msg_flags);
+	if (err)
+		ip6_flush_pending_frames(sk);
+	else if (!(msg->msg_flags & MSG_MORE))
+		err = l2tp_ip6_push_pending_frames(sk);
+	release_sock(sk);
+done:
+	dst_release(dst);
+out:
+	fl6_sock_release(flowlabel);
+	txopt_put(opt_to_free);
+
+	return err < 0 ? err : len;
+
+do_confirm:
+	if (msg->msg_flags & MSG_PROBE)
+		dst_confirm_neigh(dst, &fl6.daddr);
+	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 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 (flags & MSG_ERRQUEUE)
+		return ipv6_recv_error(sk, msg, len, addr_len);
+
+	skb = skb_recv_datagram(sk, flags, &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);
+		*addr_len = sizeof(*lsa);
+	}
+
+	if (np->rxopt.all)
+		ip6_datagram_recv_ctl(sk, msg, skb);
+
+	if (flags & MSG_TRUNC)
+		copied = skb->len;
+done:
+	skb_free_datagram(sk, skb);
+out:
+	return err ? err : copied;
+}
+
+static struct proto l2tp_ip6_prot = {
+	.name		   = "L2TP/IPv6",
+	.owner		   = THIS_MODULE,
+	.init		   = l2tp_ip6_open,
+	.close		   = l2tp_ip6_close,
+	.bind		   = l2tp_ip6_bind,
+	.connect	   = l2tp_ip6_connect,
+	.disconnect	   = l2tp_ip6_disconnect,
+	.ioctl		   = l2tp_ioctl,
+	.destroy	   = l2tp_ip6_destroy_sock,
+	.setsockopt	   = ipv6_setsockopt,
+	.getsockopt	   = ipv6_getsockopt,
+	.sendmsg	   = l2tp_ip6_sendmsg,
+	.recvmsg	   = l2tp_ip6_recvmsg,
+	.backlog_rcv	   = l2tp_ip6_backlog_recv,
+	.hash		   = l2tp_ip6_hash,
+	.unhash		   = l2tp_ip6_unhash,
+	.obj_size	   = sizeof(struct l2tp_ip6_sock),
+};
+
+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,
+	.gettstamp	   = sock_gettstamp,
+	.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_ioctl	   = inet6_compat_ioctl,
+#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 values of SOCK_DGRAM (2) as type and IPPROTO_L2TP (115) as protocol,
+ * because __stringify doesn't like enums
+ */
+MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET6, 115, 2);
+MODULE_ALIAS_NET_PF_PROTO(PF_INET6, 115);
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
new file mode 100644
index 000000000..a901fd14f
--- /dev/null
+++ b/net/l2tp/l2tp_netlink.c
@@ -0,0 +1,1048 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* 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>
+ */
+
+#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;
+
+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_get(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_get_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_get(net, tunnel_id);
+		if (tunnel) {
+			session = l2tp_tunnel_get_session(tunnel, session_id);
+			l2tp_tunnel_dec_refcount(tunnel);
+		}
+	}
+
+	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) {
+		ret = genlmsg_multicast_allns(family, msg, 0, 0, GFP_ATOMIC);
+		/* We don't care if no one is listening */
+		if (ret == -ESRCH)
+			ret = 0;
+		return ret;
+	}
+
+	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) {
+		ret = genlmsg_multicast_allns(family, msg, 0, 0, GFP_ATOMIC);
+		/* We don't care if no one is listening */
+		if (ret == -ESRCH)
+			ret = 0;
+		return ret;
+	}
+
+	nlmsg_free(msg);
+
+	return ret;
+}
+
+static int l2tp_nl_cmd_tunnel_create_get_addr(struct nlattr **attrs, struct l2tp_tunnel_cfg *cfg)
+{
+	if (attrs[L2TP_ATTR_UDP_SPORT])
+		cfg->local_udp_port = nla_get_u16(attrs[L2TP_ATTR_UDP_SPORT]);
+	if (attrs[L2TP_ATTR_UDP_DPORT])
+		cfg->peer_udp_port = nla_get_u16(attrs[L2TP_ATTR_UDP_DPORT]);
+	cfg->use_udp_checksums = nla_get_flag(attrs[L2TP_ATTR_UDP_CSUM]);
+
+	/* Must have either AF_INET or AF_INET6 address for source and destination */
+#if IS_ENABLED(CONFIG_IPV6)
+	if (attrs[L2TP_ATTR_IP6_SADDR] && attrs[L2TP_ATTR_IP6_DADDR]) {
+		cfg->local_ip6 = nla_data(attrs[L2TP_ATTR_IP6_SADDR]);
+		cfg->peer_ip6 = nla_data(attrs[L2TP_ATTR_IP6_DADDR]);
+		cfg->udp6_zero_tx_checksums = nla_get_flag(attrs[L2TP_ATTR_UDP_ZERO_CSUM6_TX]);
+		cfg->udp6_zero_rx_checksums = nla_get_flag(attrs[L2TP_ATTR_UDP_ZERO_CSUM6_RX]);
+		return 0;
+	}
+#endif
+	if (attrs[L2TP_ATTR_IP_SADDR] && attrs[L2TP_ATTR_IP_DADDR]) {
+		cfg->local_ip.s_addr = nla_get_in_addr(attrs[L2TP_ATTR_IP_SADDR]);
+		cfg->peer_ip.s_addr = nla_get_in_addr(attrs[L2TP_ATTR_IP_DADDR]);
+		return 0;
+	}
+	return -EINVAL;
+}
+
+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 = -1;
+	int ret = 0;
+	struct l2tp_tunnel_cfg cfg = { 0, };
+	struct l2tp_tunnel *tunnel;
+	struct net *net = genl_info_net(info);
+	struct nlattr **attrs = info->attrs;
+
+	if (!attrs[L2TP_ATTR_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	tunnel_id = nla_get_u32(attrs[L2TP_ATTR_CONN_ID]);
+
+	if (!attrs[L2TP_ATTR_PEER_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	peer_tunnel_id = nla_get_u32(attrs[L2TP_ATTR_PEER_CONN_ID]);
+
+	if (!attrs[L2TP_ATTR_PROTO_VERSION]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	proto_version = nla_get_u8(attrs[L2TP_ATTR_PROTO_VERSION]);
+
+	if (!attrs[L2TP_ATTR_ENCAP_TYPE]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	cfg.encap = nla_get_u16(attrs[L2TP_ATTR_ENCAP_TYPE]);
+
+	/* Managed tunnels take the tunnel socket from userspace.
+	 * Unmanaged tunnels must call out the source and destination addresses
+	 * for the kernel to create the tunnel socket itself.
+	 */
+	if (attrs[L2TP_ATTR_FD]) {
+		fd = nla_get_u32(attrs[L2TP_ATTR_FD]);
+	} else {
+		ret = l2tp_nl_cmd_tunnel_create_get_addr(attrs, &cfg);
+		if (ret < 0)
+			goto out;
+	}
+
+	ret = -EINVAL;
+	switch (cfg.encap) {
+	case L2TP_ENCAPTYPE_UDP:
+	case L2TP_ENCAPTYPE_IP:
+		ret = l2tp_tunnel_create(fd, proto_version, tunnel_id,
+					 peer_tunnel_id, &cfg, &tunnel);
+		break;
+	}
+
+	if (ret < 0)
+		goto out;
+
+	l2tp_tunnel_inc_refcount(tunnel);
+	ret = l2tp_tunnel_register(tunnel, net, &cfg);
+	if (ret < 0) {
+		kfree(tunnel);
+		goto out;
+	}
+	ret = l2tp_tunnel_notify(&l2tp_nl_family, info, tunnel,
+				 L2TP_CMD_TUNNEL_CREATE);
+	l2tp_tunnel_dec_refcount(tunnel);
+
+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_get(net, tunnel_id);
+	if (!tunnel) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	l2tp_tunnel_notify(&l2tp_nl_family, info,
+			   tunnel, L2TP_CMD_TUNNEL_DELETE);
+
+	l2tp_tunnel_delete(tunnel);
+
+	l2tp_tunnel_dec_refcount(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_get(net, tunnel_id);
+	if (!tunnel) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	ret = l2tp_tunnel_notify(&l2tp_nl_family, info,
+				 tunnel, L2TP_CMD_TUNNEL_MODIFY);
+
+	l2tp_tunnel_dec_refcount(tunnel);
+
+out:
+	return ret;
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+static int l2tp_nl_tunnel_send_addr6(struct sk_buff *skb, struct sock *sk,
+				     enum l2tp_encap_type encap)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct ipv6_pinfo *np = inet6_sk(sk);
+
+	switch (encap) {
+	case L2TP_ENCAPTYPE_UDP:
+		if (udp_get_no_check6_tx(sk) &&
+		    nla_put_flag(skb, L2TP_ATTR_UDP_ZERO_CSUM6_TX))
+			return -1;
+		if (udp_get_no_check6_rx(sk) &&
+		    nla_put_flag(skb, L2TP_ATTR_UDP_ZERO_CSUM6_RX))
+			return -1;
+		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)))
+			return -1;
+		fallthrough;
+	case L2TP_ENCAPTYPE_IP:
+		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))
+			return -1;
+		break;
+	}
+	return 0;
+}
+#endif
+
+static int l2tp_nl_tunnel_send_addr4(struct sk_buff *skb, struct sock *sk,
+				     enum l2tp_encap_type encap)
+{
+	struct inet_sock *inet = inet_sk(sk);
+
+	switch (encap) {
+	case L2TP_ENCAPTYPE_UDP:
+		if (nla_put_u8(skb, L2TP_ATTR_UDP_CSUM, !sk->sk_no_check_tx) ||
+		    nla_put_u16(skb, L2TP_ATTR_UDP_SPORT, ntohs(inet->inet_sport)) ||
+		    nla_put_u16(skb, L2TP_ATTR_UDP_DPORT, ntohs(inet->inet_dport)))
+			return -1;
+		fallthrough;
+	case L2TP_ENCAPTYPE_IP:
+		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))
+			return -1;
+		break;
+	}
+
+	return 0;
+}
+
+/* Append attributes for the tunnel address, handling the different attribute types
+ * used for different tunnel encapsulation and AF_INET v.s. AF_INET6.
+ */
+static int l2tp_nl_tunnel_send_addr(struct sk_buff *skb, struct l2tp_tunnel *tunnel)
+{
+	struct sock *sk = tunnel->sock;
+
+	if (!sk)
+		return 0;
+
+#if IS_ENABLED(CONFIG_IPV6)
+	if (sk->sk_family == AF_INET6)
+		return l2tp_nl_tunnel_send_addr6(skb, sk, tunnel->encap);
+#endif
+	return l2tp_nl_tunnel_send_addr4(skb, sk, tunnel->encap);
+}
+
+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;
+
+	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, 0) ||
+	    nla_put_u16(skb, L2TP_ATTR_ENCAP_TYPE, tunnel->encap))
+		goto nla_put_failure;
+
+	nest = nla_nest_start_noflag(skb, L2TP_ATTR_STATS);
+	if (!nest)
+		goto nla_put_failure;
+
+	if (nla_put_u64_64bit(skb, L2TP_ATTR_TX_PACKETS,
+			      atomic_long_read(&tunnel->stats.tx_packets),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_TX_BYTES,
+			      atomic_long_read(&tunnel->stats.tx_bytes),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_TX_ERRORS,
+			      atomic_long_read(&tunnel->stats.tx_errors),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_PACKETS,
+			      atomic_long_read(&tunnel->stats.rx_packets),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_BYTES,
+			      atomic_long_read(&tunnel->stats.rx_bytes),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_SEQ_DISCARDS,
+			      atomic_long_read(&tunnel->stats.rx_seq_discards),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_COOKIE_DISCARDS,
+			      atomic_long_read(&tunnel->stats.rx_cookie_discards),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_OOS_PACKETS,
+			      atomic_long_read(&tunnel->stats.rx_oos_packets),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_ERRORS,
+			      atomic_long_read(&tunnel->stats.rx_errors),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_INVALID,
+			      atomic_long_read(&tunnel->stats.rx_invalid),
+			      L2TP_ATTR_STATS_PAD))
+		goto nla_put_failure;
+	nla_nest_end(skb, nest);
+
+	if (l2tp_nl_tunnel_send_addr(skb, tunnel))
+		goto nla_put_failure;
+
+	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 err;
+	}
+
+	tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	tunnel = l2tp_tunnel_get(net, tunnel_id);
+	if (!tunnel) {
+		ret = -ENODEV;
+		goto err_nlmsg;
+	}
+
+	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_nlmsg_tunnel;
+
+	l2tp_tunnel_dec_refcount(tunnel);
+
+	return genlmsg_unicast(net, msg, info->snd_portid);
+
+err_nlmsg_tunnel:
+	l2tp_tunnel_dec_refcount(tunnel);
+err_nlmsg:
+	nlmsg_free(msg);
+err:
+	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_get_nth(net, ti);
+		if (!tunnel)
+			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) {
+			l2tp_tunnel_dec_refcount(tunnel);
+			goto out;
+		}
+		l2tp_tunnel_dec_refcount(tunnel);
+
+		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_get(net, tunnel_id);
+	if (!tunnel) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	if (!info->attrs[L2TP_ATTR_SESSION_ID]) {
+		ret = -EINVAL;
+		goto out_tunnel;
+	}
+	session_id = nla_get_u32(info->attrs[L2TP_ATTR_SESSION_ID]);
+
+	if (!info->attrs[L2TP_ATTR_PEER_SESSION_ID]) {
+		ret = -EINVAL;
+		goto out_tunnel;
+	}
+	peer_session_id = nla_get_u32(info->attrs[L2TP_ATTR_PEER_SESSION_ID]);
+
+	if (!info->attrs[L2TP_ATTR_PW_TYPE]) {
+		ret = -EINVAL;
+		goto out_tunnel;
+	}
+	cfg.pw_type = nla_get_u16(info->attrs[L2TP_ATTR_PW_TYPE]);
+	if (cfg.pw_type >= __L2TP_PWTYPE_MAX) {
+		ret = -EINVAL;
+		goto out_tunnel;
+	}
+
+	/* L2TPv2 only accepts PPP pseudo-wires */
+	if (tunnel->version == 2 && cfg.pw_type != L2TP_PWTYPE_PPP) {
+		ret = -EPROTONOSUPPORT;
+		goto out_tunnel;
+	}
+
+	if (tunnel->version > 2) {
+		if (info->attrs[L2TP_ATTR_L2SPEC_TYPE]) {
+			cfg.l2specific_type = nla_get_u8(info->attrs[L2TP_ATTR_L2SPEC_TYPE]);
+			if (cfg.l2specific_type != L2TP_L2SPECTYPE_DEFAULT &&
+			    cfg.l2specific_type != L2TP_L2SPECTYPE_NONE) {
+				ret = -EINVAL;
+				goto out_tunnel;
+			}
+		} else {
+			cfg.l2specific_type = L2TP_L2SPECTYPE_DEFAULT;
+		}
+
+		if (info->attrs[L2TP_ATTR_COOKIE]) {
+			u16 len = nla_len(info->attrs[L2TP_ATTR_COOKIE]);
+
+			if (len > 8) {
+				ret = -EINVAL;
+				goto out_tunnel;
+			}
+			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_tunnel;
+			}
+			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_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]);
+
+#ifdef CONFIG_MODULES
+	if (!l2tp_nl_cmd_ops[cfg.pw_type]) {
+		genl_unlock();
+		request_module("net-l2tp-type-%u", cfg.pw_type);
+		genl_lock();
+	}
+#endif
+	if (!l2tp_nl_cmd_ops[cfg.pw_type] || !l2tp_nl_cmd_ops[cfg.pw_type]->session_create) {
+		ret = -EPROTONOSUPPORT;
+		goto out_tunnel;
+	}
+
+	ret = l2tp_nl_cmd_ops[cfg.pw_type]->session_create(net, tunnel,
+							   session_id,
+							   peer_session_id,
+							   &cfg);
+
+	if (ret >= 0) {
+		session = l2tp_tunnel_get_session(tunnel, session_id);
+		if (session) {
+			ret = l2tp_session_notify(&l2tp_nl_family, info, session,
+						  L2TP_CMD_SESSION_CREATE);
+			l2tp_session_dec_refcount(session);
+		}
+	}
+
+out_tunnel:
+	l2tp_tunnel_dec_refcount(tunnel);
+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_get(info);
+	if (!session) {
+		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)
+			l2tp_nl_cmd_ops[pw_type]->session_delete(session);
+
+	l2tp_session_dec_refcount(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_get(info);
+	if (!session) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	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]);
+
+	ret = l2tp_session_notify(&l2tp_nl_family, info,
+				  session, L2TP_CMD_SESSION_MODIFY);
+
+	l2tp_session_dec_refcount(session);
+
+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;
+
+	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, 0) ||
+	    nla_put_u16(skb, L2TP_ATTR_PW_TYPE, session->pwtype))
+		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)) ||
+	    (session->peer_cookie_len &&
+	     nla_put(skb, L2TP_ATTR_PEER_COOKIE, session->peer_cookie_len, session->peer_cookie)) ||
+	    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) ||
+	    (l2tp_tunnel_uses_xfrm(tunnel) &&
+	     nla_put_u8(skb, L2TP_ATTR_USING_IPSEC, 1)) ||
+	    (session->reorder_timeout &&
+	     nla_put_msecs(skb, L2TP_ATTR_RECV_TIMEOUT,
+			   session->reorder_timeout, L2TP_ATTR_PAD)))
+		goto nla_put_failure;
+
+	nest = nla_nest_start_noflag(skb, L2TP_ATTR_STATS);
+	if (!nest)
+		goto nla_put_failure;
+
+	if (nla_put_u64_64bit(skb, L2TP_ATTR_TX_PACKETS,
+			      atomic_long_read(&session->stats.tx_packets),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_TX_BYTES,
+			      atomic_long_read(&session->stats.tx_bytes),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_TX_ERRORS,
+			      atomic_long_read(&session->stats.tx_errors),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_PACKETS,
+			      atomic_long_read(&session->stats.rx_packets),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_BYTES,
+			      atomic_long_read(&session->stats.rx_bytes),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_SEQ_DISCARDS,
+			      atomic_long_read(&session->stats.rx_seq_discards),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_COOKIE_DISCARDS,
+			      atomic_long_read(&session->stats.rx_cookie_discards),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_OOS_PACKETS,
+			      atomic_long_read(&session->stats.rx_oos_packets),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_ERRORS,
+			      atomic_long_read(&session->stats.rx_errors),
+			      L2TP_ATTR_STATS_PAD) ||
+	    nla_put_u64_64bit(skb, L2TP_ATTR_RX_INVALID,
+			      atomic_long_read(&session->stats.rx_invalid),
+			      L2TP_ATTR_STATS_PAD))
+		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_get(info);
+	if (!session) {
+		ret = -ENODEV;
+		goto err;
+	}
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg) {
+		ret = -ENOMEM;
+		goto err_ref;
+	}
+
+	ret = l2tp_nl_session_send(msg, info->snd_portid, info->snd_seq,
+				   0, session, L2TP_CMD_SESSION_GET);
+	if (ret < 0)
+		goto err_ref_msg;
+
+	ret = genlmsg_unicast(genl_info_net(info), msg, info->snd_portid);
+
+	l2tp_session_dec_refcount(session);
+
+	return ret;
+
+err_ref_msg:
+	nlmsg_free(msg);
+err_ref:
+	l2tp_session_dec_refcount(session);
+err:
+	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) {
+			tunnel = l2tp_tunnel_get_nth(net, ti);
+			if (!tunnel)
+				goto out;
+		}
+
+		session = l2tp_session_get_nth(tunnel, si);
+		if (!session) {
+			ti++;
+			l2tp_tunnel_dec_refcount(tunnel);
+			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) {
+			l2tp_session_dec_refcount(session);
+			l2tp_tunnel_dec_refcount(tunnel);
+			break;
+		}
+		l2tp_session_dec_refcount(session);
+
+		si++;
+	}
+
+out:
+	cb->args[0] = ti;
+	cb->args[1] = si;
+
+	return skb->len;
+}
+
+static const 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_small_ops l2tp_nl_ops[] = {
+	{
+		.cmd = L2TP_CMD_NOOP,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = l2tp_nl_cmd_noop,
+		/* can be retrieved by unprivileged users */
+	},
+	{
+		.cmd = L2TP_CMD_TUNNEL_CREATE,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = l2tp_nl_cmd_tunnel_create,
+		.flags = GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_TUNNEL_DELETE,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = l2tp_nl_cmd_tunnel_delete,
+		.flags = GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_TUNNEL_MODIFY,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = l2tp_nl_cmd_tunnel_modify,
+		.flags = GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_TUNNEL_GET,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = l2tp_nl_cmd_tunnel_get,
+		.dumpit = l2tp_nl_cmd_tunnel_dump,
+		.flags = GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_SESSION_CREATE,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = l2tp_nl_cmd_session_create,
+		.flags = GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_SESSION_DELETE,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = l2tp_nl_cmd_session_delete,
+		.flags = GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_SESSION_MODIFY,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = l2tp_nl_cmd_session_modify,
+		.flags = GENL_UNS_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_SESSION_GET,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = l2tp_nl_cmd_session_get,
+		.dumpit = l2tp_nl_cmd_session_dump,
+		.flags = GENL_UNS_ADMIN_PERM,
+	},
+};
+
+static struct genl_family l2tp_nl_family __ro_after_init = {
+	.name		= L2TP_GENL_NAME,
+	.version	= L2TP_GENL_VERSION,
+	.hdrsize	= 0,
+	.maxattr	= L2TP_ATTR_MAX,
+	.policy = l2tp_nl_policy,
+	.netnsok	= true,
+	.module		= THIS_MODULE,
+	.small_ops	= l2tp_nl_ops,
+	.n_small_ops	= ARRAY_SIZE(l2tp_nl_ops),
+	.resv_start_op	= L2TP_CMD_SESSION_GET + 1,
+	.mcgrps		= l2tp_multicast_group,
+	.n_mcgrps	= ARRAY_SIZE(l2tp_multicast_group),
+};
+
+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 __init l2tp_nl_init(void)
+{
+	pr_info("L2TP netlink interface\n");
+	return genl_register_family(&l2tp_nl_family);
+}
+
+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..f011af660
--- /dev/null
+++ b/net/l2tp/l2tp_ppp.c
@@ -0,0 +1,1743 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*****************************************************************************
+ * 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 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/ip.h>
+#include <net/udp.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 mutex		sk_lock;	/* Protects .sk */
+	struct sock __rcu	*sk;		/* Pointer to the session PPPoX socket */
+	struct sock		*__sk;		/* Copy of .sk, for cleanup */
+	struct rcu_head		rcu;		/* For asynchronous release */
+};
+
+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;
+
+/* Retrieves the pppol2tp socket associated to a session.
+ * A reference is held on the returned socket, so this function must be paired
+ * with sock_put().
+ */
+static struct sock *pppol2tp_session_get_sock(struct l2tp_session *session)
+{
+	struct pppol2tp_session *ps = l2tp_session_priv(session);
+	struct sock *sk;
+
+	rcu_read_lock();
+	sk = rcu_dereference(ps->sk);
+	if (sk)
+		sock_hold(sk);
+	rcu_read_unlock();
+
+	return sk;
+}
+
+/* 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)
+		return NULL;
+
+	sock_hold(sk);
+	session = (struct l2tp_session *)(sk->sk_user_data);
+	if (!session) {
+		sock_put(sk);
+		goto out;
+	}
+	if (WARN_ON(session->magic != L2TP_SESSION_MAGIC)) {
+		session = NULL;
+		sock_put(sk);
+		goto out;
+	}
+
+out:
+	return session;
+}
+
+/*****************************************************************************
+ * Receive data handling
+ *****************************************************************************/
+
+/* 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, &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.
+	 */
+	rcu_read_lock();
+	sk = rcu_dereference(ps->sk);
+	if (!sk)
+		goto no_sock;
+
+	/* If the first two bytes are 0xFF03, consider that it is the PPP's
+	 * Address and Control fields and skip them. The L2TP module has always
+	 * worked this way, although, in theory, the use of these fields should
+	 * be negotiated and handled at the PPP layer. These fields are
+	 * constant: 0xFF is the All-Stations Address and 0x03 the Unnumbered
+	 * Information command with Poll/Final bit set to zero (RFC 1662).
+	 */
+	if (pskb_may_pull(skb, 2) && skb->data[0] == PPP_ALLSTATIONS &&
+	    skb->data[1] == PPP_UI)
+		skb_pull(skb, 2);
+
+	if (sk->sk_state & PPPOX_BOUND) {
+		struct pppox_sock *po;
+
+		po = pppox_sk(sk);
+		ppp_input(&po->chan, skb);
+	} else {
+		if (sock_queue_rcv_skb(sk, skb) < 0) {
+			atomic_long_inc(&session->stats.rx_errors);
+			kfree_skb(skb);
+		}
+	}
+	rcu_read_unlock();
+
+	return;
+
+no_sock:
+	rcu_read_unlock();
+	pr_warn_ratelimited("%s: no socket in recv\n", session->name);
+	kfree_skb(skb);
+}
+
+/************************************************************************
+ * 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)
+{
+	struct sock *sk = sock->sk;
+	struct sk_buff *skb;
+	int error;
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel;
+	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)
+		goto error;
+
+	tunnel = session->tunnel;
+
+	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 +
+			   2 + total_len, /* 2 bytes for PPP_ALLSTATIONS & PPP_UI */
+			   0, GFP_KERNEL);
+	if (!skb)
+		goto error_put_sess;
+
+	/* 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] = PPP_ALLSTATIONS;
+	skb->data[1] = PPP_UI;
+	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;
+	}
+
+	local_bh_disable();
+	l2tp_xmit_skb(session, skb);
+	local_bh_enable();
+
+	sock_put(sk);
+
+	return total_len;
+
+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)
+{
+	struct sock *sk = (struct sock *)chan->private;
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel;
+	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)
+		goto abort;
+
+	tunnel = session->tunnel;
+
+	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 */
+		   2;			/* 2 bytes for PPP_ALLSTATIONS & PPP_UI */
+	if (skb_cow_head(skb, headroom))
+		goto abort_put_sess;
+
+	/* Setup PPP header */
+	__skb_push(skb, 2);
+	skb->data[0] = PPP_ALLSTATIONS;
+	skb->data[1] = PPP_UI;
+
+	local_bh_disable();
+	l2tp_xmit_skb(session, skb);
+	local_bh_enable();
+
+	sock_put(sk);
+
+	return 1;
+
+abort_put_sess:
+	sock_put(sk);
+abort:
+	/* Free the original skb */
+	kfree_skb(skb);
+	return 1;
+}
+
+/*****************************************************************************
+ * Session (and tunnel control) socket create/destroy.
+ *****************************************************************************/
+
+static void pppol2tp_put_sk(struct rcu_head *head)
+{
+	struct pppol2tp_session *ps;
+
+	ps = container_of(head, typeof(*ps), rcu);
+	sock_put(ps->__sk);
+}
+
+/* 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;
+
+	skb_queue_purge(&sk->sk_receive_queue);
+	skb_queue_purge(&sk->sk_write_queue);
+
+	if (session) {
+		sk->sk_user_data = NULL;
+		if (WARN_ON(session->magic != L2TP_SESSION_MAGIC))
+			return;
+		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);
+	if (session) {
+		struct pppol2tp_session *ps;
+
+		l2tp_session_delete(session);
+
+		ps = l2tp_session_priv(session);
+		mutex_lock(&ps->sk_lock);
+		ps->__sk = rcu_dereference_protected(ps->sk,
+						     lockdep_is_held(&ps->sk_lock));
+		RCU_INIT_POINTER(ps->sk, NULL);
+		mutex_unlock(&ps->sk_lock);
+		call_rcu(&ps->rcu, pppol2tp_put_sk);
+
+		/* Rely on the sock_put() call at the end of the function for
+		 * dropping the reference held by pppol2tp_sock_to_session().
+		 * The last reference will be dropped by pppol2tp_put_sk().
+		 */
+	}
+
+	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 kern)
+{
+	int error = -ENOMEM;
+	struct sock *sk;
+
+	sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pppol2tp_sk_proto, kern);
+	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;
+}
+
+static void pppol2tp_show(struct seq_file *m, void *arg)
+{
+	struct l2tp_session *session = arg;
+	struct sock *sk;
+
+	sk = pppol2tp_session_get_sock(session);
+	if (sk) {
+		struct pppox_sock *po = pppox_sk(sk);
+
+		seq_printf(m, "   interface %s\n", ppp_dev_name(&po->chan));
+		sock_put(sk);
+	}
+}
+
+static void pppol2tp_session_init(struct l2tp_session *session)
+{
+	struct pppol2tp_session *ps;
+
+	session->recv_skb = pppol2tp_recv;
+	if (IS_ENABLED(CONFIG_L2TP_DEBUGFS))
+		session->show = pppol2tp_show;
+
+	ps = l2tp_session_priv(session);
+	mutex_init(&ps->sk_lock);
+	ps->owner = current->pid;
+}
+
+struct l2tp_connect_info {
+	u8 version;
+	int fd;
+	u32 tunnel_id;
+	u32 peer_tunnel_id;
+	u32 session_id;
+	u32 peer_session_id;
+};
+
+static int pppol2tp_sockaddr_get_info(const void *sa, int sa_len,
+				      struct l2tp_connect_info *info)
+{
+	switch (sa_len) {
+	case sizeof(struct sockaddr_pppol2tp):
+	{
+		const struct sockaddr_pppol2tp *sa_v2in4 = sa;
+
+		if (sa_v2in4->sa_protocol != PX_PROTO_OL2TP)
+			return -EINVAL;
+
+		info->version = 2;
+		info->fd = sa_v2in4->pppol2tp.fd;
+		info->tunnel_id = sa_v2in4->pppol2tp.s_tunnel;
+		info->peer_tunnel_id = sa_v2in4->pppol2tp.d_tunnel;
+		info->session_id = sa_v2in4->pppol2tp.s_session;
+		info->peer_session_id = sa_v2in4->pppol2tp.d_session;
+
+		break;
+	}
+	case sizeof(struct sockaddr_pppol2tpv3):
+	{
+		const struct sockaddr_pppol2tpv3 *sa_v3in4 = sa;
+
+		if (sa_v3in4->sa_protocol != PX_PROTO_OL2TP)
+			return -EINVAL;
+
+		info->version = 3;
+		info->fd = sa_v3in4->pppol2tp.fd;
+		info->tunnel_id = sa_v3in4->pppol2tp.s_tunnel;
+		info->peer_tunnel_id = sa_v3in4->pppol2tp.d_tunnel;
+		info->session_id = sa_v3in4->pppol2tp.s_session;
+		info->peer_session_id = sa_v3in4->pppol2tp.d_session;
+
+		break;
+	}
+	case sizeof(struct sockaddr_pppol2tpin6):
+	{
+		const struct sockaddr_pppol2tpin6 *sa_v2in6 = sa;
+
+		if (sa_v2in6->sa_protocol != PX_PROTO_OL2TP)
+			return -EINVAL;
+
+		info->version = 2;
+		info->fd = sa_v2in6->pppol2tp.fd;
+		info->tunnel_id = sa_v2in6->pppol2tp.s_tunnel;
+		info->peer_tunnel_id = sa_v2in6->pppol2tp.d_tunnel;
+		info->session_id = sa_v2in6->pppol2tp.s_session;
+		info->peer_session_id = sa_v2in6->pppol2tp.d_session;
+
+		break;
+	}
+	case sizeof(struct sockaddr_pppol2tpv3in6):
+	{
+		const struct sockaddr_pppol2tpv3in6 *sa_v3in6 = sa;
+
+		if (sa_v3in6->sa_protocol != PX_PROTO_OL2TP)
+			return -EINVAL;
+
+		info->version = 3;
+		info->fd = sa_v3in6->pppol2tp.fd;
+		info->tunnel_id = sa_v3in6->pppol2tp.s_tunnel;
+		info->peer_tunnel_id = sa_v3in6->pppol2tp.d_tunnel;
+		info->session_id = sa_v3in6->pppol2tp.s_session;
+		info->peer_session_id = sa_v3in6->pppol2tp.d_session;
+
+		break;
+	}
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/* Rough estimation of the maximum payload size a tunnel can transmit without
+ * fragmenting at the lower IP layer. Assumes L2TPv2 with sequence
+ * numbers and no IP option. Not quite accurate, but the result is mostly
+ * unused anyway.
+ */
+static int pppol2tp_tunnel_mtu(const struct l2tp_tunnel *tunnel)
+{
+	int mtu;
+
+	mtu = l2tp_tunnel_dst_mtu(tunnel);
+	if (mtu <= PPPOL2TP_HEADER_OVERHEAD)
+		return 1500 - PPPOL2TP_HEADER_OVERHEAD;
+
+	return mtu - PPPOL2TP_HEADER_OVERHEAD;
+}
+
+static struct l2tp_tunnel *pppol2tp_tunnel_get(struct net *net,
+					       const struct l2tp_connect_info *info,
+					       bool *new_tunnel)
+{
+	struct l2tp_tunnel *tunnel;
+	int error;
+
+	*new_tunnel = false;
+
+	tunnel = l2tp_tunnel_get(net, info->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 (!info->session_id && !info->peer_session_id) {
+		if (!tunnel) {
+			struct l2tp_tunnel_cfg tcfg = {
+				.encap = L2TP_ENCAPTYPE_UDP,
+			};
+
+			/* Prevent l2tp_tunnel_register() from trying to set up
+			 * a kernel socket.
+			 */
+			if (info->fd < 0)
+				return ERR_PTR(-EBADF);
+
+			error = l2tp_tunnel_create(info->fd,
+						   info->version,
+						   info->tunnel_id,
+						   info->peer_tunnel_id, &tcfg,
+						   &tunnel);
+			if (error < 0)
+				return ERR_PTR(error);
+
+			l2tp_tunnel_inc_refcount(tunnel);
+			error = l2tp_tunnel_register(tunnel, net, &tcfg);
+			if (error < 0) {
+				kfree(tunnel);
+				return ERR_PTR(error);
+			}
+
+			*new_tunnel = true;
+		}
+	} else {
+		/* Error if we can't find the tunnel */
+		if (!tunnel)
+			return ERR_PTR(-ENOENT);
+
+		/* Error if socket is not prepped */
+		if (!tunnel->sock) {
+			l2tp_tunnel_dec_refcount(tunnel);
+			return ERR_PTR(-ENOENT);
+		}
+	}
+
+	return tunnel;
+}
+
+/* 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 pppox_sock *po = pppox_sk(sk);
+	struct l2tp_session *session = NULL;
+	struct l2tp_connect_info info;
+	struct l2tp_tunnel *tunnel;
+	struct pppol2tp_session *ps;
+	struct l2tp_session_cfg cfg = { 0, };
+	bool drop_refcnt = false;
+	bool new_session = false;
+	bool new_tunnel = false;
+	int error;
+
+	error = pppol2tp_sockaddr_get_info(uservaddr, sockaddr_len, &info);
+	if (error < 0)
+		return error;
+
+	/* Don't bind if tunnel_id is 0 */
+	if (!info.tunnel_id)
+		return -EINVAL;
+
+	tunnel = pppol2tp_tunnel_get(sock_net(sk), &info, &new_tunnel);
+	if (IS_ERR(tunnel))
+		return PTR_ERR(tunnel);
+
+	lock_sock(sk);
+
+	/* 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 */
+
+	if (tunnel->peer_tunnel_id == 0)
+		tunnel->peer_tunnel_id = info.peer_tunnel_id;
+
+	session = l2tp_tunnel_get_session(tunnel, info.session_id);
+	if (session) {
+		drop_refcnt = true;
+
+		if (session->pwtype != L2TP_PWTYPE_PPP) {
+			error = -EPROTOTYPE;
+			goto end;
+		}
+
+		ps = l2tp_session_priv(session);
+
+		/* Using a pre-existing session is fine as long as it hasn't
+		 * been connected yet.
+		 */
+		mutex_lock(&ps->sk_lock);
+		if (rcu_dereference_protected(ps->sk,
+					      lockdep_is_held(&ps->sk_lock)) ||
+		    ps->__sk) {
+			mutex_unlock(&ps->sk_lock);
+			error = -EEXIST;
+			goto end;
+		}
+	} else {
+		cfg.pw_type = L2TP_PWTYPE_PPP;
+
+		session = l2tp_session_create(sizeof(struct pppol2tp_session),
+					      tunnel, info.session_id,
+					      info.peer_session_id, &cfg);
+		if (IS_ERR(session)) {
+			error = PTR_ERR(session);
+			goto end;
+		}
+
+		pppol2tp_session_init(session);
+		ps = l2tp_session_priv(session);
+		l2tp_session_inc_refcount(session);
+
+		mutex_lock(&ps->sk_lock);
+		error = l2tp_session_register(session, tunnel);
+		if (error < 0) {
+			mutex_unlock(&ps->sk_lock);
+			kfree(session);
+			goto end;
+		}
+		drop_refcnt = true;
+		new_session = true;
+	}
+
+	/* 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	 = pppol2tp_tunnel_mtu(tunnel);
+
+	error = ppp_register_net_channel(sock_net(sk), &po->chan);
+	if (error) {
+		mutex_unlock(&ps->sk_lock);
+		goto end;
+	}
+
+out_no_ppp:
+	/* This is how we get the session context from the socket. */
+	sk->sk_user_data = session;
+	rcu_assign_pointer(ps->sk, sk);
+	mutex_unlock(&ps->sk_lock);
+
+	/* Keep the reference we've grabbed on the session: sk doesn't expect
+	 * the session to disappear. pppol2tp_session_destruct() is responsible
+	 * for dropping it.
+	 */
+	drop_refcnt = false;
+
+	sk->sk_state = PPPOX_CONNECTED;
+
+end:
+	if (error) {
+		if (new_session)
+			l2tp_session_delete(session);
+		if (new_tunnel)
+			l2tp_tunnel_delete(tunnel);
+	}
+	if (drop_refcnt)
+		l2tp_session_dec_refcount(session);
+	l2tp_tunnel_dec_refcount(tunnel);
+	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, struct l2tp_tunnel *tunnel,
+				   u32 session_id, u32 peer_session_id,
+				   struct l2tp_session_cfg *cfg)
+{
+	int error;
+	struct l2tp_session *session;
+
+	/* Error if tunnel socket is not prepped */
+	if (!tunnel->sock) {
+		error = -ENOENT;
+		goto err;
+	}
+
+	/* Allocate and initialize a new session context. */
+	session = l2tp_session_create(sizeof(struct pppol2tp_session),
+				      tunnel, session_id,
+				      peer_session_id, cfg);
+	if (IS_ERR(session)) {
+		error = PTR_ERR(session);
+		goto err;
+	}
+
+	pppol2tp_session_init(session);
+
+	error = l2tp_session_register(session, tunnel);
+	if (error < 0)
+		goto err_sess;
+
+	return 0;
+
+err_sess:
+	kfree(session);
+err:
+	return error;
+}
+
+#endif /* CONFIG_L2TP_V3 */
+
+/* getname() support.
+ */
+static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
+			    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)
+		goto end;
+	if (!(sk->sk_state & PPPOX_CONNECTED))
+		goto end;
+
+	error = -EBADF;
+	session = pppol2tp_sock_to_session(sk);
+	if (!session)
+		goto end;
+
+	pls = l2tp_session_priv(session);
+	tunnel = session->tunnel;
+
+	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);
+	}
+
+	error = len;
+
+	sock_put(sk);
+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,
+				const struct l2tp_stats *stats)
+{
+	memset(dest, 0, sizeof(*dest));
+
+	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);
+}
+
+static int pppol2tp_tunnel_copy_stats(struct pppol2tp_ioc_stats *stats,
+				      struct l2tp_tunnel *tunnel)
+{
+	struct l2tp_session *session;
+
+	if (!stats->session_id) {
+		pppol2tp_copy_stats(stats, &tunnel->stats);
+		return 0;
+	}
+
+	/* If session_id is set, search the corresponding session in the
+	 * context of this tunnel and record the session's statistics.
+	 */
+	session = l2tp_tunnel_get_session(tunnel, stats->session_id);
+	if (!session)
+		return -EBADR;
+
+	if (session->pwtype != L2TP_PWTYPE_PPP) {
+		l2tp_session_dec_refcount(session);
+		return -EBADR;
+	}
+
+	pppol2tp_copy_stats(stats, &session->stats);
+	l2tp_session_dec_refcount(session);
+
+	return 0;
+}
+
+static int pppol2tp_ioctl(struct socket *sock, unsigned int cmd,
+			  unsigned long arg)
+{
+	struct pppol2tp_ioc_stats stats;
+	struct l2tp_session *session;
+
+	switch (cmd) {
+	case PPPIOCGMRU:
+	case PPPIOCGFLAGS:
+		session = sock->sk->sk_user_data;
+		if (!session)
+			return -ENOTCONN;
+
+		if (WARN_ON(session->magic != L2TP_SESSION_MAGIC))
+			return -EBADF;
+
+		/* Not defined for tunnels */
+		if (!session->session_id && !session->peer_session_id)
+			return -ENOSYS;
+
+		if (put_user(0, (int __user *)arg))
+			return -EFAULT;
+		break;
+
+	case PPPIOCSMRU:
+	case PPPIOCSFLAGS:
+		session = sock->sk->sk_user_data;
+		if (!session)
+			return -ENOTCONN;
+
+		if (WARN_ON(session->magic != L2TP_SESSION_MAGIC))
+			return -EBADF;
+
+		/* Not defined for tunnels */
+		if (!session->session_id && !session->peer_session_id)
+			return -ENOSYS;
+
+		if (!access_ok((int __user *)arg, sizeof(int)))
+			return -EFAULT;
+		break;
+
+	case PPPIOCGL2TPSTATS:
+		session = sock->sk->sk_user_data;
+		if (!session)
+			return -ENOTCONN;
+
+		if (WARN_ON(session->magic != L2TP_SESSION_MAGIC))
+			return -EBADF;
+
+		/* Session 0 represents the parent tunnel */
+		if (!session->session_id && !session->peer_session_id) {
+			u32 session_id;
+			int err;
+
+			if (copy_from_user(&stats, (void __user *)arg,
+					   sizeof(stats)))
+				return -EFAULT;
+
+			session_id = stats.session_id;
+			err = pppol2tp_tunnel_copy_stats(&stats,
+							 session->tunnel);
+			if (err < 0)
+				return err;
+
+			stats.session_id = session_id;
+		} else {
+			pppol2tp_copy_stats(&stats, &session->stats);
+			stats.session_id = session->session_id;
+		}
+		stats.tunnel_id = session->tunnel->tunnel_id;
+		stats.using_ipsec = l2tp_tunnel_uses_xfrm(session->tunnel);
+
+		if (copy_to_user((void __user *)arg, &stats, sizeof(stats)))
+			return -EFAULT;
+		break;
+
+	default:
+		return -ENOIOCTLCMD;
+	}
+
+	return 0;
+}
+
+/*****************************************************************************
+ * 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 flags option is deprecated */
+		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;
+
+	switch (optname) {
+	case PPPOL2TP_SO_RECVSEQ:
+		if (val != 0 && val != 1) {
+			err = -EINVAL;
+			break;
+		}
+		session->recv_seq = !!val;
+		break;
+
+	case PPPOL2TP_SO_SENDSEQ:
+		if (val != 0 && val != 1) {
+			err = -EINVAL;
+			break;
+		}
+		session->send_seq = !!val;
+		{
+			struct pppox_sock *po = pppox_sk(sk);
+
+			po->chan.hdrlen = val ? PPPOL2TP_L2TP_HDR_SIZE_SEQ :
+				PPPOL2TP_L2TP_HDR_SIZE_NOSEQ;
+		}
+		l2tp_session_set_header_len(session, session->tunnel->version);
+		break;
+
+	case PPPOL2TP_SO_LNSMODE:
+		if (val != 0 && val != 1) {
+			err = -EINVAL;
+			break;
+		}
+		session->lns_mode = !!val;
+		break;
+
+	case PPPOL2TP_SO_DEBUG:
+		/* Session debug flags option is deprecated */
+		break;
+
+	case PPPOL2TP_SO_REORDERTO:
+		session->reorder_timeout = msecs_to_jiffies(val);
+		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,
+			       sockptr_t optval, unsigned int optlen)
+{
+	struct sock *sk = sock->sk;
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel;
+	int val;
+	int err;
+
+	if (level != SOL_PPPOL2TP)
+		return -EINVAL;
+
+	if (optlen < sizeof(int))
+		return -EINVAL;
+
+	if (copy_from_sockptr(&val, optval, sizeof(int)))
+		return -EFAULT;
+
+	err = -ENOTCONN;
+	if (!sk->sk_user_data)
+		goto end;
+
+	/* Get session context from the socket */
+	err = -EBADF;
+	session = pppol2tp_sock_to_session(sk);
+	if (!session)
+		goto end;
+
+	/* Special case: if session_id == 0x0000, treat as operation on tunnel
+	 */
+	if (session->session_id == 0 && session->peer_session_id == 0) {
+		tunnel = session->tunnel;
+		err = pppol2tp_tunnel_setsockopt(sk, tunnel, optname, val);
+	} else {
+		err = pppol2tp_session_setsockopt(sk, session, optname, val);
+	}
+
+	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:
+		/* Tunnel debug flags option is deprecated */
+		*val = 0;
+		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;
+		break;
+
+	case PPPOL2TP_SO_SENDSEQ:
+		*val = session->send_seq;
+		break;
+
+	case PPPOL2TP_SO_LNSMODE:
+		*val = session->lns_mode;
+		break;
+
+	case PPPOL2TP_SO_DEBUG:
+		/* Session debug flags option is deprecated */
+		*val = 0;
+		break;
+
+	case PPPOL2TP_SO_REORDERTO:
+		*val = (int)jiffies_to_msecs(session->reorder_timeout);
+		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;
+
+	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)
+		goto end;
+
+	/* Get the session context */
+	err = -EBADF;
+	session = pppol2tp_sock_to_session(sk);
+	if (!session)
+		goto end;
+
+	/* Special case: if session_id == 0x0000, treat as operation on tunnel */
+	if (session->session_id == 0 && session->peer_session_id == 0) {
+		tunnel = session->tunnel;
+		err = pppol2tp_tunnel_getsockopt(sk, tunnel, optname, &val);
+		if (err)
+			goto end_put_sess;
+	} else {
+		err = pppol2tp_session_getsockopt(sk, session, optname, &val);
+		if (err)
+			goto end_put_sess;
+	}
+
+	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)
+{
+	/* Drop reference taken during previous invocation */
+	if (pd->tunnel)
+		l2tp_tunnel_dec_refcount(pd->tunnel);
+
+	for (;;) {
+		pd->tunnel = l2tp_tunnel_get_nth(net, pd->tunnel_idx);
+		pd->tunnel_idx++;
+
+		/* Only accept L2TPv2 tunnels */
+		if (!pd->tunnel || pd->tunnel->version == 2)
+			return;
+
+		l2tp_tunnel_dec_refcount(pd->tunnel);
+	}
+}
+
+static void pppol2tp_next_session(struct net *net, struct pppol2tp_seq_data *pd)
+{
+	/* Drop reference taken during previous invocation */
+	if (pd->session)
+		l2tp_session_dec_refcount(pd->session);
+
+	pd->session = l2tp_session_get_nth(pd->tunnel, pd->session_idx);
+	pd->session_idx++;
+
+	if (!pd->session) {
+		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;
+
+	if (WARN_ON(!m->private)) {
+		pd = NULL;
+		goto out;
+	}
+
+	pd = m->private;
+	net = seq_file_net(m);
+
+	if (!pd->tunnel)
+		pppol2tp_next_tunnel(net, pd);
+	else
+		pppol2tp_next_session(net, pd);
+
+	/* NULL tunnel and session indicates end of list */
+	if (!pd->tunnel && !pd->session)
+		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)
+{
+	struct pppol2tp_seq_data *pd = v;
+
+	if (!pd || pd == SEQ_START_TOKEN)
+		return;
+
+	/* Drop reference taken by last invocation of pppol2tp_next_session()
+	 * or pppol2tp_next_tunnel().
+	 */
+	if (pd->session) {
+		l2tp_session_dec_refcount(pd->session);
+		pd->session = NULL;
+	}
+	if (pd->tunnel) {
+		l2tp_tunnel_dec_refcount(pd->tunnel);
+		pd->tunnel = NULL;
+	}
+}
+
+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',
+		   refcount_read(&tunnel->ref_count) - 1);
+	seq_printf(m, " %08x %ld/%ld/%ld %ld/%ld/%ld\n",
+		   0,
+		   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;
+	unsigned char state;
+	char user_data_ok;
+	struct sock *sk;
+	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);
+	}
+
+	sk = pppol2tp_session_get_sock(session);
+	if (sk) {
+		state = sk->sk_state;
+		user_data_ok = (session == sk->sk_user_data) ? 'Y' : 'N';
+	} else {
+		state = 0;
+		user_data_ok = 'N';
+	}
+
+	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,
+		   state, user_data_ok);
+	seq_printf(m, "   0/0/%c/%c/%s %08x %u\n",
+		   session->recv_seq ? 'R' : '-',
+		   session->send_seq ? 'S' : '-',
+		   session->lns_mode ? "LNS" : "LAC",
+		   0,
+		   jiffies_to_msecs(session->reorder_timeout));
+	seq_printf(m, "   %u/%u %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 (sk) {
+		struct pppox_sock *po = pppox_sk(sk);
+
+		seq_printf(m, "   interface %s\n", ppp_dev_name(&po->chan));
+		sock_put(sk);
+	}
+}
+
+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;
+	}
+
+	if (!pd->session)
+		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,
+};
+#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_net("pppol2tp", 0444, net->proc_net,
+			      &pppol2tp_seq_ops, sizeof(struct pppol2tp_seq_data));
+	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,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = pppox_compat_ioctl,
+#endif
+};
+
+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_NET_PF_PROTO(PF_PPPOX, PX_PROTO_OL2TP);
+MODULE_ALIAS_L2TP_PWTYPE(7);
diff --git a/net/l2tp/trace.h b/net/l2tp/trace.h
new file mode 100644
index 000000000..8596eaa12
--- /dev/null
+++ b/net/l2tp/trace.h
@@ -0,0 +1,211 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM l2tp
+
+#if !defined(_TRACE_L2TP_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_L2TP_H
+
+#include <linux/tracepoint.h>
+#include <linux/l2tp.h>
+#include "l2tp_core.h"
+
+#define encap_type_name(e) { L2TP_ENCAPTYPE_##e, #e }
+#define show_encap_type_name(val) \
+	__print_symbolic(val, \
+			encap_type_name(UDP), \
+			encap_type_name(IP))
+
+#define pw_type_name(p) { L2TP_PWTYPE_##p, #p }
+#define show_pw_type_name(val) \
+	__print_symbolic(val, \
+	pw_type_name(ETH_VLAN), \
+	pw_type_name(ETH), \
+	pw_type_name(PPP), \
+	pw_type_name(PPP_AC), \
+	pw_type_name(IP))
+
+DECLARE_EVENT_CLASS(tunnel_only_evt,
+	TP_PROTO(struct l2tp_tunnel *tunnel),
+	TP_ARGS(tunnel),
+	TP_STRUCT__entry(
+		__array(char, name, L2TP_TUNNEL_NAME_MAX)
+	),
+	TP_fast_assign(
+		memcpy(__entry->name, tunnel->name, L2TP_TUNNEL_NAME_MAX);
+	),
+	TP_printk("%s", __entry->name)
+);
+
+DECLARE_EVENT_CLASS(session_only_evt,
+	TP_PROTO(struct l2tp_session *session),
+	TP_ARGS(session),
+	TP_STRUCT__entry(
+		__array(char, name, L2TP_SESSION_NAME_MAX)
+	),
+	TP_fast_assign(
+		memcpy(__entry->name, session->name, L2TP_SESSION_NAME_MAX);
+	),
+	TP_printk("%s", __entry->name)
+);
+
+TRACE_EVENT(register_tunnel,
+	TP_PROTO(struct l2tp_tunnel *tunnel),
+	TP_ARGS(tunnel),
+	TP_STRUCT__entry(
+		__array(char, name, L2TP_TUNNEL_NAME_MAX)
+		__field(int, fd)
+		__field(u32, tid)
+		__field(u32, ptid)
+		__field(int, version)
+		__field(enum l2tp_encap_type, encap)
+	),
+	TP_fast_assign(
+		memcpy(__entry->name, tunnel->name, L2TP_TUNNEL_NAME_MAX);
+		__entry->fd = tunnel->fd;
+		__entry->tid = tunnel->tunnel_id;
+		__entry->ptid = tunnel->peer_tunnel_id;
+		__entry->version = tunnel->version;
+		__entry->encap = tunnel->encap;
+	),
+	TP_printk("%s: type=%s encap=%s version=L2TPv%d tid=%u ptid=%u fd=%d",
+		__entry->name,
+		__entry->fd > 0 ? "managed" : "unmanaged",
+		show_encap_type_name(__entry->encap),
+		__entry->version,
+		__entry->tid,
+		__entry->ptid,
+		__entry->fd)
+);
+
+DEFINE_EVENT(tunnel_only_evt, delete_tunnel,
+	TP_PROTO(struct l2tp_tunnel *tunnel),
+	TP_ARGS(tunnel)
+);
+
+DEFINE_EVENT(tunnel_only_evt, free_tunnel,
+	TP_PROTO(struct l2tp_tunnel *tunnel),
+	TP_ARGS(tunnel)
+);
+
+TRACE_EVENT(register_session,
+	TP_PROTO(struct l2tp_session *session),
+	TP_ARGS(session),
+	TP_STRUCT__entry(
+		__array(char, name, L2TP_SESSION_NAME_MAX)
+		__field(u32, tid)
+		__field(u32, ptid)
+		__field(u32, sid)
+		__field(u32, psid)
+		__field(enum l2tp_pwtype, pwtype)
+	),
+	TP_fast_assign(
+		memcpy(__entry->name, session->name, L2TP_SESSION_NAME_MAX);
+		__entry->tid = session->tunnel ? session->tunnel->tunnel_id : 0;
+		__entry->ptid = session->tunnel ? session->tunnel->peer_tunnel_id : 0;
+		__entry->sid = session->session_id;
+		__entry->psid = session->peer_session_id;
+		__entry->pwtype = session->pwtype;
+	),
+	TP_printk("%s: pseudowire=%s sid=%u psid=%u tid=%u ptid=%u",
+		__entry->name,
+		show_pw_type_name(__entry->pwtype),
+		__entry->sid,
+		__entry->psid,
+		__entry->sid,
+		__entry->psid)
+);
+
+DEFINE_EVENT(session_only_evt, delete_session,
+	TP_PROTO(struct l2tp_session *session),
+	TP_ARGS(session)
+);
+
+DEFINE_EVENT(session_only_evt, free_session,
+	TP_PROTO(struct l2tp_session *session),
+	TP_ARGS(session)
+);
+
+DEFINE_EVENT(session_only_evt, session_seqnum_lns_enable,
+	TP_PROTO(struct l2tp_session *session),
+	TP_ARGS(session)
+);
+
+DEFINE_EVENT(session_only_evt, session_seqnum_lns_disable,
+	TP_PROTO(struct l2tp_session *session),
+	TP_ARGS(session)
+);
+
+DECLARE_EVENT_CLASS(session_seqnum_evt,
+	TP_PROTO(struct l2tp_session *session),
+	TP_ARGS(session),
+	TP_STRUCT__entry(
+		__array(char, name, L2TP_SESSION_NAME_MAX)
+		__field(u32, ns)
+		__field(u32, nr)
+	),
+	TP_fast_assign(
+		memcpy(__entry->name, session->name, L2TP_SESSION_NAME_MAX);
+		__entry->ns = session->ns;
+		__entry->nr = session->nr;
+	),
+	TP_printk("%s: ns=%u nr=%u",
+		__entry->name,
+		__entry->ns,
+		__entry->nr)
+);
+
+DEFINE_EVENT(session_seqnum_evt, session_seqnum_update,
+	TP_PROTO(struct l2tp_session *session),
+	TP_ARGS(session)
+);
+
+DEFINE_EVENT(session_seqnum_evt, session_seqnum_reset,
+	TP_PROTO(struct l2tp_session *session),
+	TP_ARGS(session)
+);
+
+DECLARE_EVENT_CLASS(session_pkt_discard_evt,
+	TP_PROTO(struct l2tp_session *session, u32 pkt_ns),
+	TP_ARGS(session, pkt_ns),
+	TP_STRUCT__entry(
+		__array(char, name, L2TP_SESSION_NAME_MAX)
+		__field(u32, pkt_ns)
+		__field(u32, my_nr)
+		__field(u32, reorder_q_len)
+	),
+	TP_fast_assign(
+		memcpy(__entry->name, session->name, L2TP_SESSION_NAME_MAX);
+		__entry->pkt_ns = pkt_ns,
+		__entry->my_nr = session->nr;
+		__entry->reorder_q_len = skb_queue_len(&session->reorder_q);
+	),
+	TP_printk("%s: pkt_ns=%u my_nr=%u reorder_q_len=%u",
+		__entry->name,
+		__entry->pkt_ns,
+		__entry->my_nr,
+		__entry->reorder_q_len)
+);
+
+DEFINE_EVENT(session_pkt_discard_evt, session_pkt_expired,
+	TP_PROTO(struct l2tp_session *session, u32 pkt_ns),
+	TP_ARGS(session, pkt_ns)
+);
+
+DEFINE_EVENT(session_pkt_discard_evt, session_pkt_outside_rx_window,
+	TP_PROTO(struct l2tp_session *session, u32 pkt_ns),
+	TP_ARGS(session, pkt_ns)
+);
+
+DEFINE_EVENT(session_pkt_discard_evt, session_pkt_oos,
+	TP_PROTO(struct l2tp_session *session, u32 pkt_ns),
+	TP_ARGS(session, pkt_ns)
+);
+
+#endif /* _TRACE_L2TP_H */
+
+/* This part must be outside protection */
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH .
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE trace
+#include <trace/define_trace.h>