l2tp: Add netlink control API for L2TP

In L2TPv3, we need to create/delete/modify/query L2TP tunnel and
session contexts. The number of parameters is significant. So let's
use netlink. Userspace uses this API to control L2TP tunnel/session
contexts in the kernel.

The previous pppol2tp driver was managed using [gs]etsockopt(). This
API is retained for backwards compatibility. Unlike L2TPv2 which
carries only PPP frames, L2TPv3 can carry raw ethernet frames or other
frame types and these do not always have an associated socket
family. Therefore, we need a way to use L2TP sessions that doesn't
require a socket type for each supported frame type. Hence netlink is
used.

Signed-off-by: James Chapman <[e-mail]>
Reviewed-by: Randy Dunlap <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/l2tp.h

···
 #ifdef __KERNEL__
 #include <linux/socket.h>
 #include <linux/in.h>
+#else
+#include <netinet/in.h>
 #endif
 
 #define IPPROTO_L2TP		115
···
  * @l2tp_addr:    protocol specific address information
  * @l2tp_conn_id: connection id of tunnel
  */
+#define __SOCK_SIZE__	16		/* sizeof(struct sockaddr)	*/
 struct sockaddr_l2tpip {
 	/* The first fields must match struct sockaddr_in */
 	sa_family_t	l2tp_family;	/* AF_INET */
···
 			      sizeof(__be16) - sizeof(struct in_addr) -
 			      sizeof(__u32)];
 };
+
+/*****************************************************************************
+ *  NETLINK_GENERIC netlink family.
+ *****************************************************************************/
+
+/*
+ * Commands.
+ * Valid TLVs of each command are:-
+ * TUNNEL_CREATE	- CONN_ID, pw_type, netns, ifname, ipinfo, udpinfo, udpcsum, vlanid
+ * TUNNEL_DELETE	- CONN_ID
+ * TUNNEL_MODIFY	- CONN_ID, udpcsum
+ * TUNNEL_GETSTATS	- CONN_ID, (stats)
+ * TUNNEL_GET		- CONN_ID, (...)
+ * SESSION_CREATE	- SESSION_ID, PW_TYPE, offset, data_seq, cookie, peer_cookie, offset, l2spec
+ * SESSION_DELETE	- SESSION_ID
+ * SESSION_MODIFY	- SESSION_ID, data_seq
+ * SESSION_GET		- SESSION_ID, (...)
+ * SESSION_GETSTATS	- SESSION_ID, (stats)
+ *
+ */
+enum {
+	L2TP_CMD_NOOP,
+	L2TP_CMD_TUNNEL_CREATE,
+	L2TP_CMD_TUNNEL_DELETE,
+	L2TP_CMD_TUNNEL_MODIFY,
+	L2TP_CMD_TUNNEL_GET,
+	L2TP_CMD_SESSION_CREATE,
+	L2TP_CMD_SESSION_DELETE,
+	L2TP_CMD_SESSION_MODIFY,
+	L2TP_CMD_SESSION_GET,
+	__L2TP_CMD_MAX,
+};
+
+#define L2TP_CMD_MAX			(__L2TP_CMD_MAX - 1)
+
+/*
+ * ATTR types defined for L2TP
+ */
+enum {
+	L2TP_ATTR_NONE,			/* no data */
+	L2TP_ATTR_PW_TYPE,		/* u16, enum l2tp_pwtype */
+	L2TP_ATTR_ENCAP_TYPE,		/* u16, enum l2tp_encap_type */
+	L2TP_ATTR_OFFSET,		/* u16 */
+	L2TP_ATTR_DATA_SEQ,		/* u16 */
+	L2TP_ATTR_L2SPEC_TYPE,		/* u8, enum l2tp_l2spec_type */
+	L2TP_ATTR_L2SPEC_LEN,		/* u8, enum l2tp_l2spec_type */
+	L2TP_ATTR_PROTO_VERSION,	/* u8 */
+	L2TP_ATTR_IFNAME,		/* string */
+	L2TP_ATTR_CONN_ID,		/* u32 */
+	L2TP_ATTR_PEER_CONN_ID,		/* u32 */
+	L2TP_ATTR_SESSION_ID,		/* u32 */
+	L2TP_ATTR_PEER_SESSION_ID,	/* u32 */
+	L2TP_ATTR_UDP_CSUM,		/* u8 */
+	L2TP_ATTR_VLAN_ID,		/* u16 */
+	L2TP_ATTR_COOKIE,		/* 0, 4 or 8 bytes */
+	L2TP_ATTR_PEER_COOKIE,		/* 0, 4 or 8 bytes */
+	L2TP_ATTR_DEBUG,		/* u32 */
+	L2TP_ATTR_RECV_SEQ,		/* u8 */
+	L2TP_ATTR_SEND_SEQ,		/* u8 */
+	L2TP_ATTR_LNS_MODE,		/* u8 */
+	L2TP_ATTR_USING_IPSEC,		/* u8 */
+	L2TP_ATTR_RECV_TIMEOUT,		/* msec */
+	L2TP_ATTR_FD,			/* int */
+	L2TP_ATTR_IP_SADDR,		/* u32 */
+	L2TP_ATTR_IP_DADDR,		/* u32 */
+	L2TP_ATTR_UDP_SPORT,		/* u16 */
+	L2TP_ATTR_UDP_DPORT,		/* u16 */
+	L2TP_ATTR_MTU,			/* u16 */
+	L2TP_ATTR_MRU,			/* u16 */
+	L2TP_ATTR_STATS,		/* nested */
+	__L2TP_ATTR_MAX,
+};
+
+#define L2TP_ATTR_MAX			(__L2TP_ATTR_MAX - 1)
+
+/* Nested in L2TP_ATTR_STATS */
+enum {
+	L2TP_ATTR_STATS_NONE,		/* no data */
+	L2TP_ATTR_TX_PACKETS,		/* u64 */
+	L2TP_ATTR_TX_BYTES,		/* u64 */
+	L2TP_ATTR_TX_ERRORS,		/* u64 */
+	L2TP_ATTR_RX_PACKETS,		/* u64 */
+	L2TP_ATTR_RX_BYTES,		/* u64 */
+	L2TP_ATTR_RX_SEQ_DISCARDS,	/* u64 */
+	L2TP_ATTR_RX_OOS_PACKETS,	/* u64 */
+	L2TP_ATTR_RX_ERRORS,		/* u64 */
+	__L2TP_ATTR_STATS_MAX,
+};
+
+#define L2TP_ATTR_STATS_MAX		(__L2TP_ATTR_STATS_MAX - 1)
+
+enum l2tp_pwtype {
+	L2TP_PWTYPE_NONE = 0x0000,
+	L2TP_PWTYPE_ETH_VLAN = 0x0004,
+	L2TP_PWTYPE_ETH = 0x0005,
+	L2TP_PWTYPE_PPP = 0x0007,
+	L2TP_PWTYPE_PPP_AC = 0x0008,
+	L2TP_PWTYPE_IP = 0x000b,
+	__L2TP_PWTYPE_MAX
+};
+
+enum l2tp_l2spec_type {
+	L2TP_L2SPECTYPE_NONE,
+	L2TP_L2SPECTYPE_DEFAULT,
+};
+
+enum l2tp_encap_type {
+	L2TP_ENCAPTYPE_UDP,
+	L2TP_ENCAPTYPE_IP,
+};
+
+enum l2tp_seqmode {
+	L2TP_SEQ_NONE = 0,
+	L2TP_SEQ_IP = 1,
+	L2TP_SEQ_ALL = 2,
+};
+
+/*
+ * NETLINK_GENERIC related info
+ */
+#define L2TP_GENL_NAME		"l2tp"
+#define L2TP_GENL_VERSION	0x1
 
 #endif

net/l2tp/Makefile

···
 # 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

net/l2tp/l2tp_core.c

···
 #include <net/dst.h>
 #include <net/ip.h>
 #include <net/udp.h>
+#include <net/inet_common.h>
 #include <net/xfrm.h>
 #include <net/protocol.h>
 
···
 	return NULL;
 }
 EXPORT_SYMBOL_GPL(l2tp_session_find_nth);
+
+/* Lookup a session by interface name.
+ * This is very inefficient but is only used by management interfaces.
+ */
+struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname)
+{
+	struct l2tp_net *pn = l2tp_pernet(net);
+	int hash;
+	struct hlist_node *walk;
+	struct l2tp_session *session;
+
+	read_lock_bh(&pn->l2tp_session_hlist_lock);
+	for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
+		hlist_for_each_entry(session, walk, &pn->l2tp_session_hlist[hash], global_hlist) {
+			if (!strcmp(session->ifname, ifname)) {
+				read_unlock_bh(&pn->l2tp_session_hlist_lock);
+				return session;
+			}
+		}
+	}
+
+	read_unlock_bh(&pn->l2tp_session_hlist_lock);
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(l2tp_session_find_by_ifname);
 
 /* Lookup a tunnel by id
  */
···
 
 	/* Find the session context */
 	session = l2tp_session_find(tunnel->l2tp_net, tunnel, session_id);
-	if (!session) {
+	if (!session || !session->recv_skb) {
 		/* Not found? Pass to userspace to deal with */
 		PRINTK(tunnel->debug, L2TP_MSG_DATA, KERN_INFO,
 		       "%s: no session found (%u/%u). Passing up.\n",
···
 }
 EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
 
+/* This function is used by the netlink TUNNEL_DELETE command.
+ */
+int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
+{
+	int err = 0;
+
+	/* Force the tunnel socket to close. This will eventually
+	 * cause the tunnel to be deleted via the normal socket close
+	 * mechanisms when userspace closes the tunnel socket.
+	 */
+	if ((tunnel->sock != NULL) && (tunnel->sock->sk_socket != NULL))
+		err = inet_shutdown(tunnel->sock->sk_socket, 2);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
+
 /* Really kill the session.
  */
 void l2tp_session_free(struct l2tp_session *session)
···
 	return;
 }
 EXPORT_SYMBOL_GPL(l2tp_session_free);
+
+/* This function is used by the netlink SESSION_DELETE command and by
+   pseudowire modules.
+ */
+int l2tp_session_delete(struct l2tp_session *session)
+{
+	if (session->session_close != NULL)
+		(*session->session_close)(session);
+
+	l2tp_session_dec_refcount(session);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(l2tp_session_delete);
+
 
 /* We come here whenever a session's send_seq, cookie_len or
  * l2specific_len parameters are set.

net/l2tp/l2tp_core.h

···
 	L2TP_MSG_DATA		= (1 << 3),	/* data packets */
 };
 
-enum l2tp_pwtype {
-	L2TP_PWTYPE_NONE = 0x0000,
-	L2TP_PWTYPE_ETH_VLAN = 0x0004,
-	L2TP_PWTYPE_ETH = 0x0005,
-	L2TP_PWTYPE_PPP = 0x0007,
-	L2TP_PWTYPE_PPP_AC = 0x0008,
-	L2TP_PWTYPE_IP = 0x000b,
-	__L2TP_PWTYPE_MAX
-};
-
-enum l2tp_l2spec_type {
-	L2TP_L2SPECTYPE_NONE,
-	L2TP_L2SPECTYPE_DEFAULT,
-};
-
-enum l2tp_encap_type {
-	L2TP_ENCAPTYPE_UDP,
-	L2TP_ENCAPTYPE_IP,
-};
-
 struct sk_buff;
 
 struct l2tp_stats {
···
 						 * control of LNS. */
 	int			debug;		/* bitmask of debug message
 						 * categories */
+	u16			vlan_id;	/* VLAN pseudowire only */
 	u16			offset;		/* offset to payload */
 	u16			l2specific_len;	/* Layer 2 specific length */
 	u16			l2specific_type; /* Layer 2 specific type */
···
 						  * (in jiffies) */
 	int			mtu;
 	int			mru;
+	char			*ifname;
 };
 
 struct l2tp_session {
···
 	atomic_t		ref_count;
 
 	char			name[32];	/* for logging */
+	char			ifname[IFNAMSIZ];
 	unsigned		data_seq:2;	/* data sequencing level
 						 * 0 => none, 1 => IP only,
 						 * 2 => all
···
 	uint8_t			priv[0];	/* private data */
 };
 
+struct l2tp_nl_cmd_ops {
+	int (*session_create)(struct net *net, u32 tunnel_id, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg);
+	int (*session_delete)(struct l2tp_session *session);
+};
+
 static inline void *l2tp_tunnel_priv(struct l2tp_tunnel *tunnel)
 {
 	return &tunnel->priv[0];
···
 
 extern struct l2tp_session *l2tp_session_find(struct net *net, struct l2tp_tunnel *tunnel, u32 session_id);
 extern struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth);
+extern struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname);
 extern struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id);
 extern struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth);
 
 extern int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg, struct l2tp_tunnel **tunnelp);
+extern int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel);
 extern 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);
+extern int l2tp_session_delete(struct l2tp_session *session);
 extern void l2tp_tunnel_free(struct l2tp_tunnel *tunnel);
 extern void l2tp_session_free(struct l2tp_session *session);
 extern void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb, unsigned char *ptr, unsigned char *optr, u16 hdrflags, int length, int (*payload_hook)(struct sk_buff *skb));
···
 extern void l2tp_tunnel_destruct(struct sock *sk);
 extern void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel);
 extern void l2tp_session_set_header_len(struct l2tp_session *session, int version);
+
+extern int l2tp_nl_register_ops(enum l2tp_pwtype pw_type, const struct l2tp_nl_cmd_ops *ops);
+extern void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type);
 
 /* Tunnel reference counts. Incremented per session that is added to
  * the tunnel.

net/l2tp/l2tp_netlink.c

···
+/*
+ * 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 <[e-mail]>
+ * which is in turn partly based on the wireless netlink code:
+ * Copyright 2006 Johannes Berg <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <net/sock.h>
+#include <net/genetlink.h>
+#include <net/udp.h>
+#include <linux/in.h>
+#include <linux/udp.h>
+#include <linux/socket.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <net/net_namespace.h>
+
+#include <linux/l2tp.h>
+
+#include "l2tp_core.h"
+
+
+static struct genl_family l2tp_nl_family = {
+	.id		= GENL_ID_GENERATE,
+	.name		= L2TP_GENL_NAME,
+	.version	= L2TP_GENL_VERSION,
+	.hdrsize	= 0,
+	.maxattr	= L2TP_ATTR_MAX,
+};
+
+/* Accessed under genl lock */
+static const struct l2tp_nl_cmd_ops *l2tp_nl_cmd_ops[__L2TP_PWTYPE_MAX];
+
+static struct l2tp_session *l2tp_nl_session_find(struct genl_info *info)
+{
+	u32 tunnel_id;
+	u32 session_id;
+	char *ifname;
+	struct l2tp_tunnel *tunnel;
+	struct l2tp_session *session = NULL;
+	struct net *net = genl_info_net(info);
+
+	if (info->attrs[L2TP_ATTR_IFNAME]) {
+		ifname = nla_data(info->attrs[L2TP_ATTR_IFNAME]);
+		session = l2tp_session_find_by_ifname(net, ifname);
+	} else if ((info->attrs[L2TP_ATTR_SESSION_ID]) &&
+		   (info->attrs[L2TP_ATTR_CONN_ID])) {
+		tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
+		session_id = nla_get_u32(info->attrs[L2TP_ATTR_SESSION_ID]);
+		tunnel = l2tp_tunnel_find(net, tunnel_id);
+		if (tunnel)
+			session = l2tp_session_find(net, tunnel, session_id);
+	}
+
+	return session;
+}
+
+static int l2tp_nl_cmd_noop(struct sk_buff *skb, struct genl_info *info)
+{
+	struct sk_buff *msg;
+	void *hdr;
+	int ret = -ENOBUFS;
+
+	msg = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
+	if (!msg) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	hdr = genlmsg_put(msg, info->snd_pid, info->snd_seq,
+			  &l2tp_nl_family, 0, L2TP_CMD_NOOP);
+	if (IS_ERR(hdr)) {
+		ret = PTR_ERR(hdr);
+		goto err_out;
+	}
+
+	genlmsg_end(msg, hdr);
+
+	return genlmsg_unicast(genl_info_net(info), msg, info->snd_pid);
+
+err_out:
+	nlmsg_free(msg);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_cmd_tunnel_create(struct sk_buff *skb, struct genl_info *info)
+{
+	u32 tunnel_id;
+	u32 peer_tunnel_id;
+	int proto_version;
+	int fd;
+	int ret = 0;
+	struct l2tp_tunnel_cfg cfg = { 0, };
+	struct l2tp_tunnel *tunnel;
+	struct net *net = genl_info_net(info);
+
+	if (!info->attrs[L2TP_ATTR_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
+
+	if (!info->attrs[L2TP_ATTR_PEER_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	peer_tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_PEER_CONN_ID]);
+
+	if (!info->attrs[L2TP_ATTR_PROTO_VERSION]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	proto_version = nla_get_u8(info->attrs[L2TP_ATTR_PROTO_VERSION]);
+
+	if (!info->attrs[L2TP_ATTR_ENCAP_TYPE]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	cfg.encap = nla_get_u16(info->attrs[L2TP_ATTR_ENCAP_TYPE]);
+
+	if (!info->attrs[L2TP_ATTR_FD]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	fd = nla_get_u32(info->attrs[L2TP_ATTR_FD]);
+
+	if (info->attrs[L2TP_ATTR_DEBUG])
+		cfg.debug = nla_get_u32(info->attrs[L2TP_ATTR_DEBUG]);
+
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+	if (tunnel != NULL) {
+		ret = -EEXIST;
+		goto out;
+	}
+
+	ret = -EINVAL;
+	switch (cfg.encap) {
+	case L2TP_ENCAPTYPE_UDP:
+	case L2TP_ENCAPTYPE_IP:
+		ret = l2tp_tunnel_create(net, fd, proto_version, tunnel_id,
+					 peer_tunnel_id, &cfg, &tunnel);
+		break;
+	}
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_cmd_tunnel_delete(struct sk_buff *skb, struct genl_info *info)
+{
+	struct l2tp_tunnel *tunnel;
+	u32 tunnel_id;
+	int ret = 0;
+	struct net *net = genl_info_net(info);
+
+	if (!info->attrs[L2TP_ATTR_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
+
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+	if (tunnel == NULL) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	(void) l2tp_tunnel_delete(tunnel);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_cmd_tunnel_modify(struct sk_buff *skb, struct genl_info *info)
+{
+	struct l2tp_tunnel *tunnel;
+	u32 tunnel_id;
+	int ret = 0;
+	struct net *net = genl_info_net(info);
+
+	if (!info->attrs[L2TP_ATTR_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
+
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+	if (tunnel == NULL) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	if (info->attrs[L2TP_ATTR_DEBUG])
+		tunnel->debug = nla_get_u32(info->attrs[L2TP_ATTR_DEBUG]);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 pid, u32 seq, int flags,
+			       struct l2tp_tunnel *tunnel)
+{
+	void *hdr;
+	struct nlattr *nest;
+	struct sock *sk = NULL;
+	struct inet_sock *inet;
+
+	hdr = genlmsg_put(skb, pid, seq, &l2tp_nl_family, flags,
+			  L2TP_CMD_TUNNEL_GET);
+	if (IS_ERR(hdr))
+		return PTR_ERR(hdr);
+
+	NLA_PUT_U8(skb, L2TP_ATTR_PROTO_VERSION, tunnel->version);
+	NLA_PUT_U32(skb, L2TP_ATTR_CONN_ID, tunnel->tunnel_id);
+	NLA_PUT_U32(skb, L2TP_ATTR_PEER_CONN_ID, tunnel->peer_tunnel_id);
+	NLA_PUT_U32(skb, L2TP_ATTR_DEBUG, tunnel->debug);
+	NLA_PUT_U16(skb, L2TP_ATTR_ENCAP_TYPE, tunnel->encap);
+
+	nest = nla_nest_start(skb, L2TP_ATTR_STATS);
+	if (nest == NULL)
+		goto nla_put_failure;
+
+	NLA_PUT_U64(skb, L2TP_ATTR_TX_PACKETS, tunnel->stats.tx_packets);
+	NLA_PUT_U64(skb, L2TP_ATTR_TX_BYTES, tunnel->stats.tx_bytes);
+	NLA_PUT_U64(skb, L2TP_ATTR_TX_ERRORS, tunnel->stats.tx_errors);
+	NLA_PUT_U64(skb, L2TP_ATTR_RX_PACKETS, tunnel->stats.rx_packets);
+	NLA_PUT_U64(skb, L2TP_ATTR_RX_BYTES, tunnel->stats.rx_bytes);
+	NLA_PUT_U64(skb, L2TP_ATTR_RX_SEQ_DISCARDS, tunnel->stats.rx_seq_discards);
+	NLA_PUT_U64(skb, L2TP_ATTR_RX_OOS_PACKETS, tunnel->stats.rx_oos_packets);
+	NLA_PUT_U64(skb, L2TP_ATTR_RX_ERRORS, tunnel->stats.rx_errors);
+	nla_nest_end(skb, nest);
+
+	sk = tunnel->sock;
+	if (!sk)
+		goto out;
+
+	inet = inet_sk(sk);
+
+	switch (tunnel->encap) {
+	case L2TP_ENCAPTYPE_UDP:
+		NLA_PUT_U16(skb, L2TP_ATTR_UDP_SPORT, ntohs(inet->inet_sport));
+		NLA_PUT_U16(skb, L2TP_ATTR_UDP_DPORT, ntohs(inet->inet_dport));
+		NLA_PUT_U8(skb, L2TP_ATTR_UDP_CSUM, (sk->sk_no_check != UDP_CSUM_NOXMIT));
+		/* NOBREAK */
+	case L2TP_ENCAPTYPE_IP:
+		NLA_PUT_BE32(skb, L2TP_ATTR_IP_SADDR, inet->inet_saddr);
+		NLA_PUT_BE32(skb, L2TP_ATTR_IP_DADDR, inet->inet_daddr);
+		break;
+	}
+
+out:
+	return genlmsg_end(skb, hdr);
+
+nla_put_failure:
+	genlmsg_cancel(skb, hdr);
+	return -1;
+}
+
+static int l2tp_nl_cmd_tunnel_get(struct sk_buff *skb, struct genl_info *info)
+{
+	struct l2tp_tunnel *tunnel;
+	struct sk_buff *msg;
+	u32 tunnel_id;
+	int ret = -ENOBUFS;
+	struct net *net = genl_info_net(info);
+
+	if (!info->attrs[L2TP_ATTR_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
+
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+	if (tunnel == NULL) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	msg = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
+	if (!msg) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = l2tp_nl_tunnel_send(msg, info->snd_pid, info->snd_seq,
+				  NLM_F_ACK, tunnel);
+	if (ret < 0)
+		goto err_out;
+
+	return genlmsg_unicast(net, msg, info->snd_pid);
+
+err_out:
+	nlmsg_free(msg);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_cmd_tunnel_dump(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	int ti = cb->args[0];
+	struct l2tp_tunnel *tunnel;
+	struct net *net = sock_net(skb->sk);
+
+	for (;;) {
+		tunnel = l2tp_tunnel_find_nth(net, ti);
+		if (tunnel == NULL)
+			goto out;
+
+		if (l2tp_nl_tunnel_send(skb, NETLINK_CB(cb->skb).pid,
+					cb->nlh->nlmsg_seq, NLM_F_MULTI,
+					tunnel) <= 0)
+			goto out;
+
+		ti++;
+	}
+
+out:
+	cb->args[0] = ti;
+
+	return skb->len;
+}
+
+static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *info)
+{
+	u32 tunnel_id = 0;
+	u32 session_id;
+	u32 peer_session_id;
+	int ret = 0;
+	struct l2tp_tunnel *tunnel;
+	struct l2tp_session *session;
+	struct l2tp_session_cfg cfg = { 0, };
+	struct net *net = genl_info_net(info);
+
+	if (!info->attrs[L2TP_ATTR_CONN_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+	if (!tunnel) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	if (!info->attrs[L2TP_ATTR_SESSION_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	session_id = nla_get_u32(info->attrs[L2TP_ATTR_SESSION_ID]);
+	session = l2tp_session_find(net, tunnel, session_id);
+	if (session) {
+		ret = -EEXIST;
+		goto out;
+	}
+
+	if (!info->attrs[L2TP_ATTR_PEER_SESSION_ID]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	peer_session_id = nla_get_u32(info->attrs[L2TP_ATTR_PEER_SESSION_ID]);
+
+	if (!info->attrs[L2TP_ATTR_PW_TYPE]) {
+		ret = -EINVAL;
+		goto out;
+	}
+	cfg.pw_type = nla_get_u16(info->attrs[L2TP_ATTR_PW_TYPE]);
+	if (cfg.pw_type >= __L2TP_PWTYPE_MAX) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (tunnel->version > 2) {
+		if (info->attrs[L2TP_ATTR_OFFSET])
+			cfg.offset = nla_get_u16(info->attrs[L2TP_ATTR_OFFSET]);
+
+		if (info->attrs[L2TP_ATTR_DATA_SEQ])
+			cfg.data_seq = nla_get_u8(info->attrs[L2TP_ATTR_DATA_SEQ]);
+
+		cfg.l2specific_type = L2TP_L2SPECTYPE_DEFAULT;
+		if (info->attrs[L2TP_ATTR_L2SPEC_TYPE])
+			cfg.l2specific_type = nla_get_u8(info->attrs[L2TP_ATTR_L2SPEC_TYPE]);
+
+		cfg.l2specific_len = 4;
+		if (info->attrs[L2TP_ATTR_L2SPEC_LEN])
+			cfg.l2specific_len = nla_get_u8(info->attrs[L2TP_ATTR_L2SPEC_LEN]);
+
+		if (info->attrs[L2TP_ATTR_COOKIE]) {
+			u16 len = nla_len(info->attrs[L2TP_ATTR_COOKIE]);
+			if (len > 8) {
+				ret = -EINVAL;
+				goto out;
+			}
+			cfg.cookie_len = len;
+			memcpy(&cfg.cookie[0], nla_data(info->attrs[L2TP_ATTR_COOKIE]), len);
+		}
+		if (info->attrs[L2TP_ATTR_PEER_COOKIE]) {
+			u16 len = nla_len(info->attrs[L2TP_ATTR_PEER_COOKIE]);
+			if (len > 8) {
+				ret = -EINVAL;
+				goto out;
+			}
+			cfg.peer_cookie_len = len;
+			memcpy(&cfg.peer_cookie[0], nla_data(info->attrs[L2TP_ATTR_PEER_COOKIE]), len);
+		}
+		if (info->attrs[L2TP_ATTR_IFNAME])
+			cfg.ifname = nla_data(info->attrs[L2TP_ATTR_IFNAME]);
+
+		if (info->attrs[L2TP_ATTR_VLAN_ID])
+			cfg.vlan_id = nla_get_u16(info->attrs[L2TP_ATTR_VLAN_ID]);
+	}
+
+	if (info->attrs[L2TP_ATTR_DEBUG])
+		cfg.debug = nla_get_u32(info->attrs[L2TP_ATTR_DEBUG]);
+
+	if (info->attrs[L2TP_ATTR_RECV_SEQ])
+		cfg.recv_seq = nla_get_u8(info->attrs[L2TP_ATTR_RECV_SEQ]);
+
+	if (info->attrs[L2TP_ATTR_SEND_SEQ])
+		cfg.send_seq = nla_get_u8(info->attrs[L2TP_ATTR_SEND_SEQ]);
+
+	if (info->attrs[L2TP_ATTR_LNS_MODE])
+		cfg.lns_mode = nla_get_u8(info->attrs[L2TP_ATTR_LNS_MODE]);
+
+	if (info->attrs[L2TP_ATTR_RECV_TIMEOUT])
+		cfg.reorder_timeout = nla_get_msecs(info->attrs[L2TP_ATTR_RECV_TIMEOUT]);
+
+	if (info->attrs[L2TP_ATTR_MTU])
+		cfg.mtu = nla_get_u16(info->attrs[L2TP_ATTR_MTU]);
+
+	if (info->attrs[L2TP_ATTR_MRU])
+		cfg.mru = nla_get_u16(info->attrs[L2TP_ATTR_MRU]);
+
+	if ((l2tp_nl_cmd_ops[cfg.pw_type] == NULL) ||
+	    (l2tp_nl_cmd_ops[cfg.pw_type]->session_create == NULL)) {
+		ret = -EPROTONOSUPPORT;
+		goto out;
+	}
+
+	/* Check that pseudowire-specific params are present */
+	switch (cfg.pw_type) {
+	case L2TP_PWTYPE_NONE:
+		break;
+	case L2TP_PWTYPE_ETH_VLAN:
+		if (!info->attrs[L2TP_ATTR_VLAN_ID]) {
+			ret = -EINVAL;
+			goto out;
+		}
+		break;
+	case L2TP_PWTYPE_ETH:
+		break;
+	case L2TP_PWTYPE_PPP:
+	case L2TP_PWTYPE_PPP_AC:
+		break;
+	case L2TP_PWTYPE_IP:
+	default:
+		ret = -EPROTONOSUPPORT;
+		break;
+	}
+
+	ret = -EPROTONOSUPPORT;
+	if (l2tp_nl_cmd_ops[cfg.pw_type]->session_create)
+		ret = (*l2tp_nl_cmd_ops[cfg.pw_type]->session_create)(net, tunnel_id,
+			session_id, peer_session_id, &cfg);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_cmd_session_delete(struct sk_buff *skb, struct genl_info *info)
+{
+	int ret = 0;
+	struct l2tp_session *session;
+	u16 pw_type;
+
+	session = l2tp_nl_session_find(info);
+	if (session == NULL) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	pw_type = session->pwtype;
+	if (pw_type < __L2TP_PWTYPE_MAX)
+		if (l2tp_nl_cmd_ops[pw_type] && l2tp_nl_cmd_ops[pw_type]->session_delete)
+			ret = (*l2tp_nl_cmd_ops[pw_type]->session_delete)(session);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_cmd_session_modify(struct sk_buff *skb, struct genl_info *info)
+{
+	int ret = 0;
+	struct l2tp_session *session;
+
+	session = l2tp_nl_session_find(info);
+	if (session == NULL) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	if (info->attrs[L2TP_ATTR_DEBUG])
+		session->debug = nla_get_u32(info->attrs[L2TP_ATTR_DEBUG]);
+
+	if (info->attrs[L2TP_ATTR_DATA_SEQ])
+		session->data_seq = nla_get_u8(info->attrs[L2TP_ATTR_DATA_SEQ]);
+
+	if (info->attrs[L2TP_ATTR_RECV_SEQ])
+		session->recv_seq = nla_get_u8(info->attrs[L2TP_ATTR_RECV_SEQ]);
+
+	if (info->attrs[L2TP_ATTR_SEND_SEQ])
+		session->send_seq = nla_get_u8(info->attrs[L2TP_ATTR_SEND_SEQ]);
+
+	if (info->attrs[L2TP_ATTR_LNS_MODE])
+		session->lns_mode = nla_get_u8(info->attrs[L2TP_ATTR_LNS_MODE]);
+
+	if (info->attrs[L2TP_ATTR_RECV_TIMEOUT])
+		session->reorder_timeout = nla_get_msecs(info->attrs[L2TP_ATTR_RECV_TIMEOUT]);
+
+	if (info->attrs[L2TP_ATTR_MTU])
+		session->mtu = nla_get_u16(info->attrs[L2TP_ATTR_MTU]);
+
+	if (info->attrs[L2TP_ATTR_MRU])
+		session->mru = nla_get_u16(info->attrs[L2TP_ATTR_MRU]);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_session_send(struct sk_buff *skb, u32 pid, u32 seq, int flags,
+				struct l2tp_session *session)
+{
+	void *hdr;
+	struct nlattr *nest;
+	struct l2tp_tunnel *tunnel = session->tunnel;
+	struct sock *sk = NULL;
+
+	sk = tunnel->sock;
+
+	hdr = genlmsg_put(skb, pid, seq, &l2tp_nl_family, flags, L2TP_CMD_SESSION_GET);
+	if (IS_ERR(hdr))
+		return PTR_ERR(hdr);
+
+	NLA_PUT_U32(skb, L2TP_ATTR_CONN_ID, tunnel->tunnel_id);
+	NLA_PUT_U32(skb, L2TP_ATTR_SESSION_ID, session->session_id);
+	NLA_PUT_U32(skb, L2TP_ATTR_PEER_CONN_ID, tunnel->peer_tunnel_id);
+	NLA_PUT_U32(skb, L2TP_ATTR_PEER_SESSION_ID, session->peer_session_id);
+	NLA_PUT_U32(skb, L2TP_ATTR_DEBUG, session->debug);
+	NLA_PUT_U16(skb, L2TP_ATTR_PW_TYPE, session->pwtype);
+	NLA_PUT_U16(skb, L2TP_ATTR_MTU, session->mtu);
+	if (session->mru)
+		NLA_PUT_U16(skb, L2TP_ATTR_MRU, session->mru);
+
+	if (session->ifname && session->ifname[0])
+		NLA_PUT_STRING(skb, L2TP_ATTR_IFNAME, session->ifname);
+	if (session->cookie_len)
+		NLA_PUT(skb, L2TP_ATTR_COOKIE, session->cookie_len, &session->cookie[0]);
+	if (session->peer_cookie_len)
+		NLA_PUT(skb, L2TP_ATTR_PEER_COOKIE, session->peer_cookie_len, &session->peer_cookie[0]);
+	NLA_PUT_U8(skb, L2TP_ATTR_RECV_SEQ, session->recv_seq);
+	NLA_PUT_U8(skb, L2TP_ATTR_SEND_SEQ, session->send_seq);
+	NLA_PUT_U8(skb, L2TP_ATTR_LNS_MODE, session->lns_mode);
+#ifdef CONFIG_XFRM
+	if ((sk) && (sk->sk_policy[0] || sk->sk_policy[1]))
+		NLA_PUT_U8(skb, L2TP_ATTR_USING_IPSEC, 1);
+#endif
+	if (session->reorder_timeout)
+		NLA_PUT_MSECS(skb, L2TP_ATTR_RECV_TIMEOUT, session->reorder_timeout);
+
+	nest = nla_nest_start(skb, L2TP_ATTR_STATS);
+	if (nest == NULL)
+		goto nla_put_failure;
+	NLA_PUT_U64(skb, L2TP_ATTR_TX_PACKETS, session->stats.tx_packets);
+	NLA_PUT_U64(skb, L2TP_ATTR_TX_BYTES, session->stats.tx_bytes);
+	NLA_PUT_U64(skb, L2TP_ATTR_TX_ERRORS, session->stats.tx_errors);
+	NLA_PUT_U64(skb, L2TP_ATTR_RX_PACKETS, session->stats.rx_packets);
+	NLA_PUT_U64(skb, L2TP_ATTR_RX_BYTES, session->stats.rx_bytes);
+	NLA_PUT_U64(skb, L2TP_ATTR_RX_SEQ_DISCARDS, session->stats.rx_seq_discards);
+	NLA_PUT_U64(skb, L2TP_ATTR_RX_OOS_PACKETS, session->stats.rx_oos_packets);
+	NLA_PUT_U64(skb, L2TP_ATTR_RX_ERRORS, session->stats.rx_errors);
+	nla_nest_end(skb, nest);
+
+	return genlmsg_end(skb, hdr);
+
+ nla_put_failure:
+	genlmsg_cancel(skb, hdr);
+	return -1;
+}
+
+static int l2tp_nl_cmd_session_get(struct sk_buff *skb, struct genl_info *info)
+{
+	struct l2tp_session *session;
+	struct sk_buff *msg;
+	int ret;
+
+	session = l2tp_nl_session_find(info);
+	if (session == NULL) {
+		ret = -ENODEV;
+		goto out;
+	}
+
+	msg = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
+	if (!msg) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = l2tp_nl_session_send(msg, info->snd_pid, info->snd_seq,
+				   0, session);
+	if (ret < 0)
+		goto err_out;
+
+	return genlmsg_unicast(genl_info_net(info), msg, info->snd_pid);
+
+err_out:
+	nlmsg_free(msg);
+
+out:
+	return ret;
+}
+
+static int l2tp_nl_cmd_session_dump(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	struct net *net = sock_net(skb->sk);
+	struct l2tp_session *session;
+	struct l2tp_tunnel *tunnel = NULL;
+	int ti = cb->args[0];
+	int si = cb->args[1];
+
+	for (;;) {
+		if (tunnel == NULL) {
+			tunnel = l2tp_tunnel_find_nth(net, ti);
+			if (tunnel == NULL)
+				goto out;
+		}
+
+		session = l2tp_session_find_nth(tunnel, si);
+		if (session == NULL) {
+			ti++;
+			tunnel = NULL;
+			si = 0;
+			continue;
+		}
+
+		if (l2tp_nl_session_send(skb, NETLINK_CB(cb->skb).pid,
+					 cb->nlh->nlmsg_seq, NLM_F_MULTI,
+					 session) <= 0)
+			break;
+
+		si++;
+	}
+
+out:
+	cb->args[0] = ti;
+	cb->args[1] = si;
+
+	return skb->len;
+}
+
+static struct nla_policy l2tp_nl_policy[L2TP_ATTR_MAX + 1] = {
+	[L2TP_ATTR_NONE]		= { .type = NLA_UNSPEC, },
+	[L2TP_ATTR_PW_TYPE]		= { .type = NLA_U16, },
+	[L2TP_ATTR_ENCAP_TYPE]		= { .type = NLA_U16, },
+	[L2TP_ATTR_OFFSET]		= { .type = NLA_U16, },
+	[L2TP_ATTR_DATA_SEQ]		= { .type = NLA_U8, },
+	[L2TP_ATTR_L2SPEC_TYPE]		= { .type = NLA_U8, },
+	[L2TP_ATTR_L2SPEC_LEN]		= { .type = NLA_U8, },
+	[L2TP_ATTR_PROTO_VERSION]	= { .type = NLA_U8, },
+	[L2TP_ATTR_CONN_ID]		= { .type = NLA_U32, },
+	[L2TP_ATTR_PEER_CONN_ID]	= { .type = NLA_U32, },
+	[L2TP_ATTR_SESSION_ID]		= { .type = NLA_U32, },
+	[L2TP_ATTR_PEER_SESSION_ID]	= { .type = NLA_U32, },
+	[L2TP_ATTR_UDP_CSUM]		= { .type = NLA_U8, },
+	[L2TP_ATTR_VLAN_ID]		= { .type = NLA_U16, },
+	[L2TP_ATTR_DEBUG]		= { .type = NLA_U32, },
+	[L2TP_ATTR_RECV_SEQ]		= { .type = NLA_U8, },
+	[L2TP_ATTR_SEND_SEQ]		= { .type = NLA_U8, },
+	[L2TP_ATTR_LNS_MODE]		= { .type = NLA_U8, },
+	[L2TP_ATTR_USING_IPSEC]		= { .type = NLA_U8, },
+	[L2TP_ATTR_RECV_TIMEOUT]	= { .type = NLA_MSECS, },
+	[L2TP_ATTR_FD]			= { .type = NLA_U32, },
+	[L2TP_ATTR_IP_SADDR]		= { .type = NLA_U32, },
+	[L2TP_ATTR_IP_DADDR]		= { .type = NLA_U32, },
+	[L2TP_ATTR_UDP_SPORT]		= { .type = NLA_U16, },
+	[L2TP_ATTR_UDP_DPORT]		= { .type = NLA_U16, },
+	[L2TP_ATTR_MTU]			= { .type = NLA_U16, },
+	[L2TP_ATTR_MRU]			= { .type = NLA_U16, },
+	[L2TP_ATTR_STATS]		= { .type = NLA_NESTED, },
+	[L2TP_ATTR_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 struct genl_ops l2tp_nl_ops[] = {
+	{
+		.cmd = L2TP_CMD_NOOP,
+		.doit = l2tp_nl_cmd_noop,
+		.policy = l2tp_nl_policy,
+		/* can be retrieved by unprivileged users */
+	},
+	{
+		.cmd = L2TP_CMD_TUNNEL_CREATE,
+		.doit = l2tp_nl_cmd_tunnel_create,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_TUNNEL_DELETE,
+		.doit = l2tp_nl_cmd_tunnel_delete,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_TUNNEL_MODIFY,
+		.doit = l2tp_nl_cmd_tunnel_modify,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_TUNNEL_GET,
+		.doit = l2tp_nl_cmd_tunnel_get,
+		.dumpit = l2tp_nl_cmd_tunnel_dump,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_SESSION_CREATE,
+		.doit = l2tp_nl_cmd_session_create,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_SESSION_DELETE,
+		.doit = l2tp_nl_cmd_session_delete,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_SESSION_MODIFY,
+		.doit = l2tp_nl_cmd_session_modify,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd = L2TP_CMD_SESSION_GET,
+		.doit = l2tp_nl_cmd_session_get,
+		.dumpit = l2tp_nl_cmd_session_dump,
+		.policy = l2tp_nl_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
+};
+
+int l2tp_nl_register_ops(enum l2tp_pwtype pw_type, const struct l2tp_nl_cmd_ops *ops)
+{
+	int ret;
+
+	ret = -EINVAL;
+	if (pw_type >= __L2TP_PWTYPE_MAX)
+		goto err;
+
+	genl_lock();
+	ret = -EBUSY;
+	if (l2tp_nl_cmd_ops[pw_type])
+		goto out;
+
+	l2tp_nl_cmd_ops[pw_type] = ops;
+
+out:
+	genl_unlock();
+err:
+	return 0;
+}
+EXPORT_SYMBOL_GPL(l2tp_nl_register_ops);
+
+void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type)
+{
+	if (pw_type < __L2TP_PWTYPE_MAX) {
+		genl_lock();
+		l2tp_nl_cmd_ops[pw_type] = NULL;
+		genl_unlock();
+	}
+}
+EXPORT_SYMBOL_GPL(l2tp_nl_unregister_ops);
+
+static int l2tp_nl_init(void)
+{
+	int err;
+
+	printk(KERN_INFO "L2TP netlink interface\n");
+	err = genl_register_family_with_ops(&l2tp_nl_family, l2tp_nl_ops,
+					    ARRAY_SIZE(l2tp_nl_ops));
+
+	return err;
+}
+
+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 <[e-mail]>");
+MODULE_DESCRIPTION("L2TP netlink");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("1.0");
+MODULE_ALIAS("net-pf-" __stringify(PF_NETLINK) "-proto-" \
+	     __stringify(NETLINK_GENERIC) "-type-" "l2tp")

net/l2tp/l2tp_ppp.c

···
 #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>
···
 	if (tunnel_id == 0)
 		goto end;
 
+	tunnel = l2tp_tunnel_find(sock_net(sk), tunnel_id);
+
 	/* Special case: create tunnel context if session_id and
 	 * peer_session_id is 0. Otherwise look up tunnel using supplied
 	 * tunnel id.
 	 */
 	if ((session_id == 0) && (peer_session_id == 0)) {
-		error = l2tp_tunnel_create(sock_net(sk), fd, ver, tunnel_id, peer_tunnel_id, NULL, &tunnel);
-		if (error < 0)
-			goto end;
+		if (tunnel == NULL) {
+			struct l2tp_tunnel_cfg tcfg = {
+				.encap = L2TP_ENCAPTYPE_UDP,
+				.debug = 0,
+			};
+			error = l2tp_tunnel_create(sock_net(sk), fd, ver, tunnel_id, peer_tunnel_id, &tcfg, &tunnel);
+			if (error < 0)
+				goto end;
+		}
 	} else {
-		tunnel = l2tp_tunnel_find(sock_net(sk), tunnel_id);
-
 		/* Error if we can't find the tunnel */
 		error = -ENOENT;
 		if (tunnel == NULL)
···
 	if (tunnel->recv_payload_hook == NULL)
 		tunnel->recv_payload_hook = pppol2tp_recv_payload_hook;
 
-	/* Check that this session doesn't already exist */
-	error = -EEXIST;
-	session = l2tp_session_find(sock_net(sk), tunnel, session_id);
-	if (session != NULL)
-		goto end;
-
-	/* Default MTU values. */
-	if (cfg.mtu == 0)
-		cfg.mtu = 1500 - PPPOL2TP_HEADER_OVERHEAD;
-	if (cfg.mru == 0)
-		cfg.mru = cfg.mtu;
-	cfg.debug = tunnel->debug;
-
-	/* Allocate and initialize a new session context. */
-	session = l2tp_session_create(sizeof(struct pppol2tp_session),
-				      tunnel, session_id,
-				      peer_session_id, &cfg);
-	if (session == NULL) {
-		error = -ENOMEM;
-		goto end;
+	if (tunnel->peer_tunnel_id == 0) {
+		if (ver == 2)
+			tunnel->peer_tunnel_id = sp->pppol2tp.d_tunnel;
+		else
+			tunnel->peer_tunnel_id = sp3->pppol2tp.d_tunnel;
 	}
 
+	/* Create session if it doesn't already exist. We handle the
+	 * case where a session was previously created by the netlink
+	 * interface by checking that the session doesn't already have
+	 * a socket and its tunnel socket are what we expect. If any
+	 * of those checks fail, return EEXIST to the caller.
+	 */
+	session = l2tp_session_find(sock_net(sk), tunnel, session_id);
+	if (session == NULL) {
+		/* Default MTU must allow space for UDP/L2TP/PPP
+		 * headers.
+		 */
+		cfg.mtu = cfg.mru = 1500 - PPPOL2TP_HEADER_OVERHEAD;
+
+		/* Allocate and initialize a new session context. */
+		session = l2tp_session_create(sizeof(struct pppol2tp_session),
+					      tunnel, session_id,
+					      peer_session_id, &cfg);
+		if (session == NULL) {
+			error = -ENOMEM;
+			goto end;
+		}
+	} else {
+		ps = l2tp_session_priv(session);
+		error = -EEXIST;
+		if (ps->sock != NULL)
+			goto end;
+
+		/* consistency checks */
+		if (ps->tunnel_sock != tunnel->sock)
+			goto end;
+	}
+
+	/* Associate session with its PPPoL2TP socket */
 	ps = l2tp_session_priv(session);
 	ps->owner	     = current->pid;
 	ps->sock	     = sk;
···
 
 	return error;
 }
+
+#ifdef CONFIG_L2TP_V3
+
+/* Called when creating sessions via the netlink interface.
+ */
+static int pppol2tp_session_create(struct net *net, u32 tunnel_id, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg)
+{
+	int error;
+	struct l2tp_tunnel *tunnel;
+	struct l2tp_session *session;
+	struct pppol2tp_session *ps;
+
+	tunnel = l2tp_tunnel_find(net, tunnel_id);
+
+	/* Error if we can't find the tunnel */
+	error = -ENOENT;
+	if (tunnel == NULL)
+		goto out;
+
+	/* Error if tunnel socket is not prepped */
+	if (tunnel->sock == NULL)
+		goto out;
+
+	/* Check that this session doesn't already exist */
+	error = -EEXIST;
+	session = l2tp_session_find(net, tunnel, session_id);
+	if (session != NULL)
+		goto out;
+
+	/* Default MTU values. */
+	if (cfg->mtu == 0)
+		cfg->mtu = 1500 - PPPOL2TP_HEADER_OVERHEAD;
+	if (cfg->mru == 0)
+		cfg->mru = cfg->mtu;
+
+	/* Allocate and initialize a new session context. */
+	error = -ENOMEM;
+	session = l2tp_session_create(sizeof(struct pppol2tp_session),
+				      tunnel, session_id,
+				      peer_session_id, cfg);
+	if (session == NULL)
+		goto out;
+
+	ps = l2tp_session_priv(session);
+	ps->tunnel_sock = tunnel->sock;
+
+	PRINTK(session->debug, PPPOL2TP_MSG_CONTROL, KERN_INFO,
+	       "%s: created\n", session->name);
+
+	error = 0;
+
+out:
+	return error;
+}
+
+/* Called when deleting sessions via the netlink interface.
+ */
+static int pppol2tp_session_delete(struct l2tp_session *session)
+{
+	struct pppol2tp_session *ps = l2tp_session_priv(session);
+
+	if (ps->sock == NULL)
+		l2tp_session_dec_refcount(session);
+
+	return 0;
+}
+
+#endif /* CONFIG_L2TP_V3 */
 
 /* getname() support.
  */
···
 	.ioctl		= pppol2tp_ioctl
 };
 
+#ifdef CONFIG_L2TP_V3
+
+static const struct l2tp_nl_cmd_ops pppol2tp_nl_cmd_ops = {
+	.session_create	= pppol2tp_session_create,
+	.session_delete	= pppol2tp_session_delete,
+};
+
+#endif /* CONFIG_L2TP_V3 */
+
 static int __init pppol2tp_init(void)
 {
 	int err;
···
 	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
+
 	printk(KERN_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:
···
 
 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);