text: /*
   * L2TPv3 IP encapsulation support
   *
   * Copyright (c) 2008,2009,2010 Katalix Systems Ltd
   *
   *	This program is free software; you can redistribute it and/or
   *	modify it under the terms of the GNU General Public License
   *	as published by the Free Software Foundation; either version
   *	2 of the License, or (at your option) any later version.
   */
  
  #include <linux/icmp.h>
  #include <linux/module.h>
  #include <linux/skbuff.h>
  #include <linux/random.h>
  #include <linux/socket.h>
  #include <linux/l2tp.h>
  #include <linux/in.h>
  #include <net/sock.h>
  #include <net/ip.h>
  #include <net/icmp.h>
  #include <net/udp.h>
  #include <net/inet_common.h>
  #include <net/inet_hashtables.h>
  #include <net/tcp_states.h>
  #include <net/protocol.h>
  #include <net/xfrm.h>
  
  #include "l2tp_core.h"
  
  struct l2tp_ip_sock {
  	/* inet_sock has to be the first member of l2tp_ip_sock */
  	struct inet_sock	inet;
  
  	__u32			conn_id;
  	__u32			peer_conn_id;
  
  	__u64			tx_packets;
  	__u64			tx_bytes;
  	__u64			tx_errors;
  	__u64			rx_packets;
  	__u64			rx_bytes;
  	__u64			rx_errors;
  };
  
  static DEFINE_RWLOCK(l2tp_ip_lock);
  static struct hlist_head l2tp_ip_table;
  static struct hlist_head l2tp_ip_bind_table;
  
  static inline struct l2tp_ip_sock *l2tp_ip_sk(const struct sock *sk)
  {
  	return (struct l2tp_ip_sock *)sk;
  }
  
  static struct sock *__l2tp_ip_bind_lookup(struct net *net, __be32 laddr, int dif, u32 tunnel_id)
  {
  	struct hlist_node *node;
  	struct sock *sk;
  
  	sk_for_each_bound(sk, node, &l2tp_ip_bind_table) {
  		struct inet_sock *inet = inet_sk(sk);
  		struct l2tp_ip_sock *l2tp = l2tp_ip_sk(sk);
  
  		if (l2tp == NULL)
  			continue;
  
  		if ((l2tp->conn_id == tunnel_id) &&
  		    net_eq(sock_net(sk), net) &&
  		    !(inet->inet_rcv_saddr && inet->inet_rcv_saddr != laddr) &&
  		    !(sk->sk_bound_dev_if && sk->sk_bound_dev_if != dif))
  			goto found;
  	}
  
  	sk = NULL;
  found:
  	return sk;
  }
  
  static inline struct sock *l2tp_ip_bind_lookup(struct net *net, __be32 laddr, int dif, u32 tunnel_id)
  {
  	struct sock *sk = __l2tp_ip_bind_lookup(net, laddr, dif, tunnel_id);
  	if (sk)
  		sock_hold(sk);
  
  	return sk;
  }
  
  /* When processing receive frames, there are two cases to
   * consider. Data frames consist of a non-zero session-id and an
   * optional cookie. Control frames consist of a regular L2TP header
   * preceded by 32-bits of zeros.
   *
   * L2TPv3 Session Header Over IP
   *
   *  0                   1                   2                   3
   *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |                           Session ID                          |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |               Cookie (optional, maximum 64 bits)...
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   *                                                                 |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   *
   * L2TPv3 Control Message Header Over IP
   *
   *  0                   1                   2                   3
   *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |                      (32 bits of zeros)                       |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |T|L|x|x|S|x|x|x|x|x|x|x|  Ver  |             Length            |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |                     Control Connection ID                     |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * |               Ns              |               Nr              |
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   *
   * All control frames are passed to userspace.
   */
  static int l2tp_ip_recv(struct sk_buff *skb)
  {
  	struct sock *sk;
  	u32 session_id;
  	u32 tunnel_id;
  	unsigned char *ptr, *optr;
  	struct l2tp_session *session;
  	struct l2tp_tunnel *tunnel = NULL;
  	int length;
  	int offset;
  
  	/* Point to L2TP header */
  	optr = ptr = skb->data;
  
  	if (!pskb_may_pull(skb, 4))
  		goto discard;
  
  	session_id = ntohl(*((__be32 *) ptr));
  	ptr += 4;
  
  	/* RFC3931: L2TP/IP packets have the first 4 bytes containing
  	 * the session_id. If it is 0, the packet is a L2TP control
  	 * frame and the session_id value can be discarded.
  	 */
  	if (session_id == 0) {
  		__skb_pull(skb, 4);
  		goto pass_up;
  	}
  
  	/* Ok, this is a data packet. Lookup the session. */
  	session = l2tp_session_find(&init_net, NULL, session_id);
  	if (session == NULL)
  		goto discard;
  
  	tunnel = session->tunnel;
  	if (tunnel == NULL)
  		goto discard;
  
  	/* Trace packet contents, if enabled */
  	if (tunnel->debug & L2TP_MSG_DATA) {
  		length = min(32u, skb->len);
  		if (!pskb_may_pull(skb, length))
  			goto discard;
  
  		printk(KERN_DEBUG "%s: ip recv: ", tunnel->name);
  
  		offset = 0;
  		do {
  			printk(" %02X", ptr[offset]);
  		} while (++offset < length);
  
  		printk("\n");
  	}
  
  	l2tp_recv_common(session, skb, ptr, optr, 0, skb->len, tunnel->recv_payload_hook);
  
  	return 0;
  
  pass_up:
  	/* Get the tunnel_id from the L2TP header */
  	if (!pskb_may_pull(skb, 12))
  		goto discard;
  
  	if ((skb->data[0] & 0xc0) != 0xc0)
  		goto discard;
  
  	tunnel_id = ntohl(*(__be32 *) &skb->data[4]);
  	tunnel = l2tp_tunnel_find(&init_net, tunnel_id);
  	if (tunnel != NULL)
  		sk = tunnel->sock;
  	else {
  		struct iphdr *iph = (struct iphdr *) skb_network_header(skb);
  
  		read_lock_bh(&l2tp_ip_lock);
  		sk = __l2tp_ip_bind_lookup(&init_net, iph->daddr, 0, tunnel_id);
  		read_unlock_bh(&l2tp_ip_lock);
  	}
  
  	if (sk == NULL)
  		goto discard;
  
  	sock_hold(sk);
  
  	if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
  		goto discard_put;
  
  	nf_reset(skb);
  
  	return sk_receive_skb(sk, skb, 1);
  
  discard_put:
  	sock_put(sk);
  
  discard:
  	kfree_skb(skb);
  	return 0;
  }
  
  static int l2tp_ip_open(struct sock *sk)
  {
  	/* Prevent autobind. We don't have ports. */
  	inet_sk(sk)->inet_num = IPPROTO_L2TP;
  
  	write_lock_bh(&l2tp_ip_lock);
  	sk_add_node(sk, &l2tp_ip_table);
  	write_unlock_bh(&l2tp_ip_lock);
  
  	return 0;
  }
  
  static void l2tp_ip_close(struct sock *sk, long timeout)
  {
  	write_lock_bh(&l2tp_ip_lock);
  	hlist_del_init(&sk->sk_bind_node);
  	sk_del_node_init(sk);
  	write_unlock_bh(&l2tp_ip_lock);
  	sk_common_release(sk);
  }
  
  static void l2tp_ip_destroy_sock(struct sock *sk)
  {
  	struct sk_buff *skb;
  
  	while ((skb = __skb_dequeue_tail(&sk->sk_write_queue)) != NULL)
  		kfree_skb(skb);
  
  	sk_refcnt_debug_dec(sk);
  }
  
  static int l2tp_ip_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len)
  {
  	struct inet_sock *inet = inet_sk(sk);
  	struct sockaddr_l2tpip *addr = (struct sockaddr_l2tpip *) uaddr;
  	int ret = -EINVAL;
  	int chk_addr_ret;
  
  	ret = -EADDRINUSE;
  	read_lock_bh(&l2tp_ip_lock);
  	if (__l2tp_ip_bind_lookup(&init_net, addr->l2tp_addr.s_addr, sk->sk_bound_dev_if, addr->l2tp_conn_id))
  		goto out_in_use;
  
  	read_unlock_bh(&l2tp_ip_lock);
  
  	lock_sock(sk);
  	if (sk->sk_state != TCP_CLOSE || addr_len < sizeof(struct sockaddr_l2tpip))
  		goto out;
  
  	chk_addr_ret = inet_addr_type(&init_net, addr->l2tp_addr.s_addr);
  	ret = -EADDRNOTAVAIL;
  	if (addr->l2tp_addr.s_addr && chk_addr_ret != RTN_LOCAL &&
  	    chk_addr_ret != RTN_MULTICAST && chk_addr_ret != RTN_BROADCAST)
  		goto out;
  
  	if (addr->l2tp_addr.s_addr)
  		inet->inet_rcv_saddr = inet->inet_saddr = addr->l2tp_addr.s_addr;
  	if (chk_addr_ret == RTN_MULTICAST || chk_addr_ret == RTN_BROADCAST)
  		inet->inet_saddr = 0;  /* Use device */
  	sk_dst_reset(sk);
  
  	l2tp_ip_sk(sk)->conn_id = addr->l2tp_conn_id;
  
  	write_lock_bh(&l2tp_ip_lock);
  	sk_add_bind_node(sk, &l2tp_ip_bind_table);
  	sk_del_node_init(sk);
  	write_unlock_bh(&l2tp_ip_lock);
  	ret = 0;
  out:
  	release_sock(sk);
  
  	return ret;
  
  out_in_use:
  	read_unlock_bh(&l2tp_ip_lock);
  
  	return ret;
  }
  
  static int l2tp_ip_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
  {
  	struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *) uaddr;
  	struct inet_sock *inet = inet_sk(sk);
  	struct flowi4 *fl4;
  	struct rtable *rt;
  	__be32 saddr;
  	int oif, rc;
  
  	rc = -EINVAL;
  	if (addr_len < sizeof(*lsa))
  		goto out;
  
  	rc = -EAFNOSUPPORT;
  	if (lsa->l2tp_family != AF_INET)
  		goto out;
  
  	lock_sock(sk);
  
  	sk_dst_reset(sk);
  
  	oif = sk->sk_bound_dev_if;
  	saddr = inet->inet_saddr;
  
  	rc = -EINVAL;
  	if (ipv4_is_multicast(lsa->l2tp_addr.s_addr))
  		goto out;
  
  	fl4 = &inet->cork.fl.u.ip4;
  	rt = ip_route_connect(fl4, lsa->l2tp_addr.s_addr, saddr,
  			      RT_CONN_FLAGS(sk), oif,
  			      IPPROTO_L2TP,
  			      0, 0, sk, true);
  	if (IS_ERR(rt)) {
  		rc = PTR_ERR(rt);
  		if (rc == -ENETUNREACH)
  			IP_INC_STATS_BH(&init_net, IPSTATS_MIB_OUTNOROUTES);
  		goto out;
  	}
  
  	rc = -ENETUNREACH;
  	if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
  		ip_rt_put(rt);
  		goto out;
  	}
  
  	l2tp_ip_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;
  
  	if (!inet->inet_saddr)
  		inet->inet_saddr = fl4->saddr;
  	if (!inet->inet_rcv_saddr)
  		inet->inet_rcv_saddr = fl4->saddr;
  	inet->inet_daddr = fl4->daddr;
  	sk->sk_state = TCP_ESTABLISHED;
  	inet->inet_id = jiffies;
  
  	sk_dst_set(sk, &rt->dst);
  
  	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);
  
  	rc = 0;
  out:
  	release_sock(sk);
  	return rc;
  }
  
  static int l2tp_ip_getname(struct socket *sock, struct sockaddr *uaddr,
  			   int *uaddr_len, int peer)
  {
  	struct sock *sk		= sock->sk;
  	struct inet_sock *inet	= inet_sk(sk);
  	struct l2tp_ip_sock *lsk = l2tp_ip_sk(sk);
  	struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *)uaddr;
  
  	memset(lsa, 0, sizeof(*lsa));
  	lsa->l2tp_family = AF_INET;
  	if (peer) {
  		if (!inet->inet_dport)
  			return -ENOTCONN;
  		lsa->l2tp_conn_id = lsk->peer_conn_id;
  		lsa->l2tp_addr.s_addr = inet->inet_daddr;
  	} else {
  		__be32 addr = inet->inet_rcv_saddr;
  		if (!addr)
  			addr = inet->inet_saddr;
  		lsa->l2tp_conn_id = lsk->conn_id;
  		lsa->l2tp_addr.s_addr = addr;
  	}
  	*uaddr_len = sizeof(*lsa);
  	return 0;
  }
  
  static int l2tp_ip_backlog_recv(struct sock *sk, struct sk_buff *skb)
  {
  	int rc;
  
  	/* Charge it to the socket, dropping if the queue is full. */
  	rc = sock_queue_rcv_skb(sk, skb);
  	if (rc < 0)
  		goto drop;
  
  	return 0;
  
  drop:
  	IP_INC_STATS(&init_net, IPSTATS_MIB_INDISCARDS);
  	kfree_skb(skb);
  	return -1;
  }
  
  /* Userspace will call sendmsg() on the tunnel socket to send L2TP
   * control frames.
   */
  static int l2tp_ip_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg, size_t len)
  {
  	struct sk_buff *skb;
  	int rc;
  	struct l2tp_ip_sock *lsa = l2tp_ip_sk(sk);
  	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) {
  		struct sockaddr_l2tpip *lip = (struct sockaddr_l2tpip *) 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_fromiovec(skb_put(skb, len), msg->msg_iov, len);
  	if (rc < 0) {
  		kfree_skb(skb);
  		goto error;
  	}
  
  	fl4 = &inet->cork.fl.u.ip4;
  	if (connected)
  		rt = (struct rtable *) __sk_dst_check(sk, 0);
  
  	rcu_read_lock();
  	if (rt == NULL) {
  		const struct ip_options_rcu *inet_opt;
  
  		inet_opt = rcu_dereference(inet->inet_opt);
  
  		/* Use correct destination address if we have options. */
  		if (inet_opt && inet_opt->opt.srr)
  			daddr = inet_opt->opt.faddr;
  
  		/* If this fails, retransmit mechanism of transport layer will
  		 * keep trying until route appears or the connection times
  		 * itself out.
  		 */
  		rt = ip_route_output_ports(sock_net(sk), fl4, sk,
  					   daddr, inet->inet_saddr,
  					   inet->inet_dport, inet->inet_sport,
  					   sk->sk_protocol, RT_CONN_FLAGS(sk),
  					   sk->sk_bound_dev_if);
  		if (IS_ERR(rt))
  			goto no_route;
  		if (connected)
  			sk_setup_caps(sk, &rt->dst);
  		else
  			dst_release(&rt->dst); /* safe since we hold rcu_read_lock */
  	}
  
  	/* We dont need to clone dst here, it is guaranteed to not disappear.
  	 *  __dev_xmit_skb() might force a refcount if needed.
  	 */
  	skb_dst_set_noref(skb, &rt->dst);
  
  	/* Queue the packet to IP for output */
  	rc = ip_queue_xmit(skb, &inet->cork.fl);
  	rcu_read_unlock();
  
  error:
  	/* Update stats */
  	if (rc >= 0) {
  		lsa->tx_packets++;
  		lsa->tx_bytes += len;
  		rc = len;
  	} else {
  		lsa->tx_errors++;
  	}
  
  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 kiocb *iocb, struct sock *sk, struct msghdr *msg,
  			   size_t len, int noblock, int flags, int *addr_len)
  {
  	struct inet_sock *inet = inet_sk(sk);
  	struct l2tp_ip_sock *lsk = l2tp_ip_sk(sk);
  	size_t copied = 0;
  	int err = -EOPNOTSUPP;
  	struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name;
  	struct sk_buff *skb;
  
  	if (flags & MSG_OOB)
  		goto out;
  
  	if (addr_len)
  		*addr_len = sizeof(*sin);
  
  	skb = skb_recv_datagram(sk, flags, noblock, &err);
  	if (!skb)
  		goto out;
  
  	copied = skb->len;
  	if (len < copied) {
  		msg->msg_flags |= MSG_TRUNC;
  		copied = len;
  	}
  
  	err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, 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));
  	}
  	if (inet->cmsg_flags)
  		ip_cmsg_recv(msg, skb);
  	if (flags & MSG_TRUNC)
  		copied = skb->len;
  done:
  	skb_free_datagram(sk, skb);
  out:
  	if (err) {
  		lsk->rx_errors++;
  		return err;
  	}
  
  	lsk->rx_packets++;
  	lsk->rx_bytes += copied;
  
  	return copied;
  }
  
  static struct proto l2tp_ip_prot = {
  	.name		   = "L2TP/IP",
  	.owner		   = THIS_MODULE,
  	.init		   = l2tp_ip_open,
  	.close		   = l2tp_ip_close,
  	.bind		   = l2tp_ip_bind,
  	.connect	   = l2tp_ip_connect,
  	.disconnect	   = udp_disconnect,
  	.ioctl		   = udp_ioctl,
  	.destroy	   = l2tp_ip_destroy_sock,
  	.setsockopt	   = ip_setsockopt,
  	.getsockopt	   = ip_getsockopt,
  	.sendmsg	   = l2tp_ip_sendmsg,
  	.recvmsg	   = l2tp_ip_recvmsg,
  	.backlog_rcv	   = l2tp_ip_backlog_recv,
  	.hash		   = inet_hash,
  	.unhash		   = inet_unhash,
  	.obj_size	   = sizeof(struct l2tp_ip_sock),
  #ifdef CONFIG_COMPAT
  	.compat_setsockopt = compat_ip_setsockopt,
  	.compat_getsockopt = compat_ip_getsockopt,
  #endif
  };
  
  static const struct proto_ops l2tp_ip_ops = {
  	.family		   = PF_INET,
  	.owner		   = THIS_MODULE,
  	.release	   = inet_release,
  	.bind		   = inet_bind,
  	.connect	   = inet_dgram_connect,
  	.socketpair	   = sock_no_socketpair,
  	.accept		   = sock_no_accept,
  	.getname	   = l2tp_ip_getname,
  	.poll		   = datagram_poll,
  	.ioctl		   = inet_ioctl,
  	.listen		   = sock_no_listen,
  	.shutdown	   = inet_shutdown,
  	.setsockopt	   = sock_common_setsockopt,
  	.getsockopt	   = sock_common_getsockopt,
  	.sendmsg	   = inet_sendmsg,
  	.recvmsg	   = sock_common_recvmsg,
  	.mmap		   = sock_no_mmap,
  	.sendpage	   = sock_no_sendpage,
  #ifdef CONFIG_COMPAT
  	.compat_setsockopt = compat_sock_common_setsockopt,
  	.compat_getsockopt = compat_sock_common_getsockopt,
  #endif
  };
  
  static struct inet_protosw l2tp_ip_protosw = {
  	.type		= SOCK_DGRAM,
  	.protocol	= IPPROTO_L2TP,
  	.prot		= &l2tp_ip_prot,
  	.ops		= &l2tp_ip_ops,
  	.no_check	= 0,
  };
  
  static struct net_protocol l2tp_ip_protocol __read_mostly = {
  	.handler	= l2tp_ip_recv,
  };
  
  static int __init l2tp_ip_init(void)
  {
  	int err;
  
  	printk(KERN_INFO "L2TP IP encapsulation support (L2TPv3)\n");
  
  	err = proto_register(&l2tp_ip_prot, 1);
  	if (err != 0)
  		goto out;
  
  	err = inet_add_protocol(&l2tp_ip_protocol, IPPROTO_L2TP);
  	if (err)
  		goto out1;
  
  	inet_register_protosw(&l2tp_ip_protosw);
  	return 0;
  
  out1:
  	proto_unregister(&l2tp_ip_prot);
  out:
  	return err;
  }
  
  static void __exit l2tp_ip_exit(void)
  {
  	inet_unregister_protosw(&l2tp_ip_protosw);
  	inet_del_protocol(&l2tp_ip_protocol, IPPROTO_L2TP);
  	proto_unregister(&l2tp_ip_prot);
  }
  
  module_init(l2tp_ip_init);
  module_exit(l2tp_ip_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
  MODULE_DESCRIPTION("L2TP over IP");
  MODULE_VERSION("1.0");
  
  /* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like
   * enums
   */
  MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 2, IPPROTO_L2TP);
  