/*
   * L2TP internal definitions.
   *
   * Copyright (c) 2008,2009 Katalix Systems Ltd
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   */
  
  #ifndef _L2TP_CORE_H_
  #define _L2TP_CORE_H_
  
  /* Just some random numbers */
  #define L2TP_TUNNEL_MAGIC	0x42114DDA
  #define L2TP_SESSION_MAGIC	0x0C04EB7D

  /* Per tunnel, session hash table size */

  #define L2TP_HASH_BITS	4
  #define L2TP_HASH_SIZE	(1 << L2TP_HASH_BITS)

  /* System-wide, session hash table size */
  #define L2TP_HASH_BITS_2	8
  #define L2TP_HASH_SIZE_2	(1 << L2TP_HASH_BITS_2)

  /* Debug message categories for the DEBUG socket option */
  enum {
  	L2TP_MSG_DEBUG		= (1 << 0),	/* verbose debug (if
  						 * compiled in) */
  	L2TP_MSG_CONTROL	= (1 << 1),	/* userspace - kernel
  						 * interface */
  	L2TP_MSG_SEQ		= (1 << 2),	/* sequence numbers */
  	L2TP_MSG_DATA		= (1 << 3),	/* data packets */
  };
  
  struct sk_buff;
  
  struct l2tp_stats {

  	atomic_long_t		tx_packets;
  	atomic_long_t		tx_bytes;
  	atomic_long_t		tx_errors;
  	atomic_long_t		rx_packets;
  	atomic_long_t		rx_bytes;
  	atomic_long_t		rx_seq_discards;
  	atomic_long_t		rx_oos_packets;
  	atomic_long_t		rx_errors;
  	atomic_long_t		rx_cookie_discards;

  };
  
  struct l2tp_tunnel;
  
  /* Describes a session. Contains information to determine incoming
   * packets and transmit outgoing ones.
   */
  struct l2tp_session_cfg {

  	enum l2tp_pwtype	pw_type;

  	unsigned int		data_seq:2;	/* data sequencing level

  						 * 0 => none, 1 => IP only,
  						 * 2 => all
  						 */

  	unsigned int		recv_seq:1;	/* expect receive packets with

  						 * sequence numbers? */

  	unsigned int		send_seq:1;	/* send packets with sequence

  						 * numbers? */

  	unsigned int		lns_mode:1;	/* behave as LNS? LAC enables

  						 * sequence numbers under
  						 * control of LNS. */
  	int			debug;		/* bitmask of debug message
  						 * categories */

  	u16			vlan_id;	/* VLAN pseudowire only */

  	u16			offset;		/* offset to payload */
  	u16			l2specific_len;	/* Layer 2 specific length */
  	u16			l2specific_type; /* Layer 2 specific type */
  	u8			cookie[8];	/* optional cookie */
  	int			cookie_len;	/* 0, 4 or 8 bytes */
  	u8			peer_cookie[8];	/* peer's cookie */
  	int			peer_cookie_len; /* 0, 4 or 8 bytes */

  	int			reorder_timeout; /* configured reorder timeout
  						  * (in jiffies) */
  	int			mtu;
  	int			mru;

  	char			*ifname;

  };
  
  struct l2tp_session {
  	int			magic;		/* should be
  						 * L2TP_SESSION_MAGIC */
  
  	struct l2tp_tunnel	*tunnel;	/* back pointer to tunnel
  						 * context */
  	u32			session_id;
  	u32			peer_session_id;

  	u8			cookie[8];
  	int			cookie_len;
  	u8			peer_cookie[8];
  	int			peer_cookie_len;
  	u16			offset;		/* offset from end of L2TP header
  						   to beginning of data */
  	u16			l2specific_len;
  	u16			l2specific_type;
  	u16			hdr_len;
  	u32			nr;		/* session NR state (receive) */
  	u32			ns;		/* session NR state (send) */

  	struct sk_buff_head	reorder_q;	/* receive reorder queue */

  	u32			nr_max;		/* max NR. Depends on tunnel */
  	u32			nr_window_size;	/* NR window size */

  	u32			nr_oos;		/* NR of last OOS packet */
  	int			nr_oos_count;	/* For OOS recovery */
  	int			nr_oos_count_max;

  	struct hlist_node	hlist;		/* Hash list node */
  	atomic_t		ref_count;
  
  	char			name[32];	/* for logging */

  	char			ifname[IFNAMSIZ];

  	unsigned int		data_seq:2;	/* data sequencing level

  						 * 0 => none, 1 => IP only,
  						 * 2 => all
  						 */

  	unsigned int		recv_seq:1;	/* expect receive packets with

  						 * sequence numbers? */

  	unsigned int		send_seq:1;	/* send packets with sequence

  						 * numbers? */

  	unsigned int		lns_mode:1;	/* behave as LNS? LAC enables

  						 * sequence numbers under
  						 * control of LNS. */
  	int			debug;		/* bitmask of debug message
  						 * categories */
  	int			reorder_timeout; /* configured reorder timeout
  						  * (in jiffies) */

  	int			reorder_skip;	/* set if skip to next nr */

  	int			mtu;
  	int			mru;

  	enum l2tp_pwtype	pwtype;

  	struct l2tp_stats	stats;

  	struct hlist_node	global_hlist;	/* Global hash list node */

  	int (*build_header)(struct l2tp_session *session, void *buf);

  	void (*recv_skb)(struct l2tp_session *session, struct sk_buff *skb, int data_len);
  	void (*session_close)(struct l2tp_session *session);
  	void (*ref)(struct l2tp_session *session);
  	void (*deref)(struct l2tp_session *session);

  #if IS_ENABLED(CONFIG_L2TP_DEBUGFS)

  	void (*show)(struct seq_file *m, void *priv);
  #endif

  	uint8_t			priv[0];	/* private data */
  };
  
  /* Describes the tunnel. It contains info to track all the associated
   * sessions so incoming packets can be sorted out
   */
  struct l2tp_tunnel_cfg {
  	int			debug;		/* bitmask of debug message
  						 * categories */

  	enum l2tp_encap_type	encap;

  
  	/* Used only for kernel-created sockets */
  	struct in_addr		local_ip;
  	struct in_addr		peer_ip;

  #if IS_ENABLED(CONFIG_IPV6)
  	struct in6_addr		*local_ip6;
  	struct in6_addr		*peer_ip6;
  #endif

  	u16			local_udp_port;
  	u16			peer_udp_port;

  	unsigned int		use_udp_checksums:1,
  				udp6_zero_tx_checksums:1,
  				udp6_zero_rx_checksums:1;

  };
  
  struct l2tp_tunnel {
  	int			magic;		/* Should be L2TP_TUNNEL_MAGIC */

  
  	unsigned long		dead;

  	struct rcu_head rcu;

  	rwlock_t		hlist_lock;	/* protect session_hlist */
  	struct hlist_head	session_hlist[L2TP_HASH_SIZE];
  						/* hashed list of sessions,
  						 * hashed by id */
  	u32			tunnel_id;
  	u32			peer_tunnel_id;
  	int			version;	/* 2=>L2TPv2, 3=>L2TPv3 */
  
  	char			name[20];	/* for logging */
  	int			debug;		/* bitmask of debug message
  						 * categories */

  	enum l2tp_encap_type	encap;

  	struct l2tp_stats	stats;
  
  	struct list_head	list;		/* Keep a list of all tunnels */
  	struct net		*l2tp_net;	/* the net we belong to */
  
  	atomic_t		ref_count;

  #ifdef CONFIG_DEBUG_FS
  	void (*show)(struct seq_file *m, void *arg);
  #endif

  	int (*recv_payload_hook)(struct sk_buff *skb);
  	void (*old_sk_destruct)(struct sock *);
  	struct sock		*sock;		/* Parent socket */

  	int			fd;		/* Parent fd, if tunnel socket
  						 * was created by userspace */

  #if IS_ENABLED(CONFIG_IPV6)
  	bool			v4mapped;
  #endif

  	struct work_struct	del_work;

  	uint8_t			priv[0];	/* private data */
  };

  struct l2tp_nl_cmd_ops {
  	int (*session_create)(struct net *net, u32 tunnel_id, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg);
  	int (*session_delete)(struct l2tp_session *session);
  };

  static inline void *l2tp_tunnel_priv(struct l2tp_tunnel *tunnel)
  {
  	return &tunnel->priv[0];
  }
  
  static inline void *l2tp_session_priv(struct l2tp_session *session)
  {
  	return &session->priv[0];
  }
  
  static inline struct l2tp_tunnel *l2tp_sock_to_tunnel(struct sock *sk)
  {
  	struct l2tp_tunnel *tunnel;
  
  	if (sk == NULL)
  		return NULL;
  
  	sock_hold(sk);
  	tunnel = (struct l2tp_tunnel *)(sk->sk_user_data);
  	if (tunnel == NULL) {
  		sock_put(sk);
  		goto out;
  	}
  
  	BUG_ON(tunnel->magic != L2TP_TUNNEL_MAGIC);
  
  out:
  	return tunnel;
  }

  struct l2tp_session *l2tp_session_get(struct net *net,
  				      struct l2tp_tunnel *tunnel,
  				      u32 session_id, bool do_ref);

  struct l2tp_session *l2tp_session_find(struct net *net,
  				       struct l2tp_tunnel *tunnel,
  				       u32 session_id);

  struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth,
  					  bool do_ref);

  struct l2tp_session *l2tp_session_get_by_ifname(struct net *net, char *ifname,
  						bool do_ref);

  struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id);
  struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth);
  
  int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id,
  		       u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg,
  		       struct l2tp_tunnel **tunnelp);
  void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel);

  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);
  void __l2tp_session_unhash(struct l2tp_session *session);
  int l2tp_session_delete(struct l2tp_session *session);
  void l2tp_session_free(struct l2tp_session *session);
  void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
  		      unsigned char *ptr, unsigned char *optr, u16 hdrflags,
  		      int length, int (*payload_hook)(struct sk_buff *skb));
  int l2tp_session_queue_purge(struct l2tp_session *session);
  int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb);

  void l2tp_session_set_header_len(struct l2tp_session *session, int version);

  
  int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb,
  		  int hdr_len);
  
  int l2tp_nl_register_ops(enum l2tp_pwtype pw_type,
  			 const struct l2tp_nl_cmd_ops *ops);
  void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type);

  int l2tp_ioctl(struct sock *sk, int cmd, unsigned long arg);

  /* Session reference counts. Incremented when code obtains a reference
   * to a session.
   */
  static inline void l2tp_session_inc_refcount_1(struct l2tp_session *session)
  {
  	atomic_inc(&session->ref_count);
  }
  
  static inline void l2tp_session_dec_refcount_1(struct l2tp_session *session)
  {
  	if (atomic_dec_and_test(&session->ref_count))
  		l2tp_session_free(session);
  }
  
  #ifdef L2TP_REFCNT_DEBUG

  #define l2tp_session_inc_refcount(_s)					\
  do {									\
  	pr_debug("l2tp_session_inc_refcount: %s:%d %s: cnt=%d
  ",	\
  		 __func__, __LINE__, (_s)->name,			\
  		 atomic_read(&_s->ref_count));				\
  	l2tp_session_inc_refcount_1(_s);				\
  } while (0)
  #define l2tp_session_dec_refcount(_s)					\
  do {									\
  	pr_debug("l2tp_session_dec_refcount: %s:%d %s: cnt=%d
  ",	\
  		 __func__, __LINE__, (_s)->name,			\
  		 atomic_read(&_s->ref_count));				\
  	l2tp_session_dec_refcount_1(_s);				\
  } while (0)

  #else
  #define l2tp_session_inc_refcount(s) l2tp_session_inc_refcount_1(s)
  #define l2tp_session_dec_refcount(s) l2tp_session_dec_refcount_1(s)
  #endif

  #define l2tp_printk(ptr, type, func, fmt, ...)				\
  do {									\
  	if (((ptr)->debug) & (type))					\
  		func(fmt, ##__VA_ARGS__);				\
  } while (0)
  
  #define l2tp_warn(ptr, type, fmt, ...)					\
  	l2tp_printk(ptr, type, pr_warn, fmt, ##__VA_ARGS__)
  #define l2tp_info(ptr, type, fmt, ...)					\
  	l2tp_printk(ptr, type, pr_info, fmt, ##__VA_ARGS__)
  #define l2tp_dbg(ptr, type, fmt, ...)					\
  	l2tp_printk(ptr, type, pr_debug, fmt, ##__VA_ARGS__)

  #define MODULE_ALIAS_L2TP_PWTYPE(type) \
  	MODULE_ALIAS("net-l2tp-type-" __stringify(type))

  #endif /* _L2TP_CORE_H_ */