text: /** @file
   *  @brief Bluetooth connection handling
   */
  
  /*
   * Copyright (c) 2015-2016 Intel Corporation
   *
   * SPDX-License-Identifier: Apache-2.0
   */
  #ifndef __BT_CONN_H
  #define __BT_CONN_H
  
  /**
   * @brief Connection management
   * @defgroup bt_conn Connection management
   * @ingroup bluetooth
   * @{
   */
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  #include <stdbool.h>
  
  #include <bluetooth/bluetooth.h>
  #include <bluetooth/hci.h>
  
  /** Opaque type representing a connection to a remote device */
  struct bt_conn;
  
  /** Connection parameters for LE connections */
  struct bt_le_conn_param {
  	uint16_t interval_min;
  	uint16_t interval_max;
  	uint16_t latency;
  	uint16_t timeout;
  };
  
  /** Helper to declare connection parameters inline
    *
    * @param int_min  Minimum Connection Interval (N * 1.25 ms)
    * @param int_max  Maximum Connection Interval (N * 1.25 ms)
    * @param lat      Connection Latency
    * @param to       Supervision Timeout (N * 10 ms)
    */
  #define BT_LE_CONN_PARAM(int_min, int_max, lat, to) \
  	(&(struct bt_le_conn_param) { \
  		.interval_min = (int_min), \
  		.interval_max = (int_max), \
  		.latency = (lat), \
  		.timeout = (to), \
  	 })
  
  /** Default LE connection parameters:
    *   Connection Interval: 30-50 ms
    *   Latency: 0
    *   Timeout: 4 s
    */
  #define BT_LE_CONN_PARAM_DEFAULT BT_LE_CONN_PARAM(BT_GAP_INIT_CONN_INT_MIN, \
  						  BT_GAP_INIT_CONN_INT_MAX, \
  						  0, 400)
  
  /** @brief Increment a connection's reference count.
   *
   *  Increment the reference count of a connection object.
   *
   *  @param conn Connection object.
   *
   *  @return Connection object with incremented reference count.
   */
  struct bt_conn *bt_conn_ref(struct bt_conn *conn);
  
  /** @brief Decrement a connection's reference count.
   *
   *  Decrement the reference count of a connection object.
   *
   *  @param conn Connection object.
   */
  void bt_conn_unref(struct bt_conn *conn);
  
  /** @brief Look up an existing connection by address.
   *
   *  Look up an existing connection based on the remote address.
   *
   *  @param peer Remote address.
   *
   *  @return Connection object or NULL if not found. The caller gets a
   *  new reference to the connection object which must be released with
   *  bt_conn_unref() once done using the object.
   */
  struct bt_conn *bt_conn_lookup_addr_le(const bt_addr_le_t *peer);
  
  /** @brief Get destination (peer) address of a connection.
   *
   *  @param conn Connection object.
   *
   *  @return Destination address.
   */
  const bt_addr_le_t *bt_conn_get_dst(const struct bt_conn *conn);
  
  /** Connection Type */
  enum {
  	/** LE Connection Type */
  	BT_CONN_TYPE_LE,
  	/** BR/EDR Connection Type */
  	BT_CONN_TYPE_BR,
  };
  
  /** LE Connection Info Structure */
  struct bt_conn_le_info {
  	const bt_addr_le_t *src; /** Source Address */
  	const bt_addr_le_t *dst; /** Destination Address */
  	uint16_t interval; /** Connection interval */
  	uint16_t latency; /** Connection slave latency */
  	uint16_t timeout; /** Connection supervision timeout */
  };
  
  /** BR/EDR Connection Info Structure */
  struct bt_conn_br_info {
  	const bt_addr_t *dst; /** Destination BR/EDR address */
  };
  
  /** Connection role (master or slave) */
  enum {
  	BT_CONN_ROLE_MASTER,
  	BT_CONN_ROLE_SLAVE,
  };
  
  /** @brief Connection Info Structure
   *
   *
   *  @param type Connection Type
   *  @param role Connection Role
   *  @param le LE Connection specific Info
   *  @param br BR/EDR Connection specific Info
   */
  struct bt_conn_info {
  	uint8_t type;
  
  	uint8_t role;
  
  	union {
  		struct bt_conn_le_info le;
  
  		struct bt_conn_br_info br;
  	};
  };
  
  /** @brief Get connection info
   *
   *  @param conn Connection object.
   *  @param info Connection info object.
   *
   *  @return Zero on success or (negative) error code on failure.
   */
  int bt_conn_get_info(const struct bt_conn *conn, struct bt_conn_info *info);
  
  /** @brief Update the connection parameters.
   *
   *  @param conn Connection object.
   *  @param param Updated connection parameters.
   *
   *  @return Zero on success or (negative) error code on failure.
   */
  int bt_conn_le_param_update(struct bt_conn *conn,
  			    const struct bt_le_conn_param *param);
  
  /** @brief Disconnect from a remote device or cancel pending connection.
   *
   *  Disconnect an active connection with the specified reason code or cancel
   *  pending outgoing connection.
   *
   *  @param conn Connection to disconnect.
   *  @param reason Reason code for the disconnection.
   *
   *  @return Zero on success or (negative) error code on failure.
   */
  int bt_conn_disconnect(struct bt_conn *conn, uint8_t reason);
  
  /** @brief Initiate an LE connection to a remote device.
   *
   *  Allows initiate new LE link to remote peer using its address.
   *  Returns a new reference that the the caller is responsible for managing.
   *
   *  @param peer  Remote address.
   *  @param param Initial connection parameters.
   *
   *  @return Valid connection object on success or NULL otherwise.
   */
  struct bt_conn *bt_conn_create_le(const bt_addr_le_t *peer,
  				  const struct bt_le_conn_param *param);
  
  /** @brief Automatically connect to remote device if it's in range.
   *
   *  This function enables/disables automatic connection initiation.
   *  Everytime the device looses the connection with peer, this connection
   *  will be re-established if connectable advertisement from peer is received.
   *
   *  @param addr Remote Bluetooth address.
   *  @param param If non-NULL, auto connect is enabled with the given
   *  parameters. If NULL, auto connect is disabled.
   *
   *  @return Zero on success or error code otherwise.
   */
  int bt_le_set_auto_conn(bt_addr_le_t *addr,
  			const struct bt_le_conn_param *param);
  
  /** @brief Initiate directed advertising to a remote device
   *
   *  Allows initiating a new LE connection to remote peer with the remote
   *  acting in central role and the local device in peripheral role.
   *
   *  The advertising type must be either BT_LE_ADV_DIRECT_IND or
   *  BT_LE_ADV_DIRECT_IND_LOW_DUTY.
   *
   *  In case of high duty cycle this will result in a callback with
   *  connected() with a new connection or with an error.
   *
   *  The advertising may be cancelled with bt_conn_disconnect().
   *
   *  Returns a new reference that the the caller is responsible for managing.
   *
   *  @param peer  Remote address.
   *  @param param Directed advertising parameters.
   *
   *  @return Valid connection object on success or NULL otherwise.
   */
  struct bt_conn *bt_conn_create_slave_le(const bt_addr_le_t *peer,
  					const struct bt_le_adv_param *param);
  
  /** Security level. */
  typedef enum __packed {
  	/** Only for BR/EDR special cases, like SDP */
  	BT_SECURITY_NONE,
  	/** No encryption and no authentication. */
  	BT_SECURITY_LOW,
  	/** Encryption and no authentication (no MITM). */
  	BT_SECURITY_MEDIUM,
  	/** Encryption and authentication (MITM). */
  	BT_SECURITY_HIGH,
  	/** Authenticated Secure Connections */
  	BT_SECURITY_FIPS,
  } bt_security_t;
  
  /** @brief Set security level for a connection.
   *
   *  This function enable security (encryption) for a connection. If device is
   *  already paired with sufficiently strong key encryption will be enabled. If
   *  link is already encrypted with sufficiently strong key this function does
   *  nothing.
   *
   *  If device is not paired pairing will be initiated. If device is paired and
   *  keys are too weak but input output capabilities allow for strong enough keys
   *  pairing will be initiated.
   *
   *  This function may return error if required level of security is not possible
   *  to achieve due to local or remote device limitation (eg input output
   *  capabilities).
   *
   *  @param conn Connection object.
   *  @param sec Requested security level.
   *
   *  @return 0 on success or negative error
   */
  int bt_conn_security(struct bt_conn *conn, bt_security_t sec);
  
  /** @brief Get encryption key size.
   *
   *  This function gets encryption key size.
   *  If there is no security (encryption) enabled 0 will be returned.
   *
   *  @param conn Existing connection object.
   *
   *  @return Encryption key size.
   */
  uint8_t bt_conn_enc_key_size(struct bt_conn *conn);
  
  /** @brief Connection callback structure.
   *
   *  This structure is used for tracking the state of a connection.
   *  It is registered with the help of the bt_conn_cb_register() API.
   *  It's premissible to register multiple instances of this @ref bt_conn_cb
   *  type, in case different modules of an application are interested in
   *  tracking the connection state. If a callback is not of interest for
   *  an instance, it may be set to NULL and will as a consequence not be
   *  used for that instance.
   */
  struct bt_conn_cb {
  	/** @brief A new connection has been established.
  	 *
  	 *  This callback notifies the application of a new connection.
  	 *  In case the err parameter is non-zero it means that the
  	 *  connection establishment failed.
  	 *
  	 *  @param conn New connection object.
  	 *  @param err HCI error. Zero for success, non-zero otherwise.
  	 */
  	void (*connected)(struct bt_conn *conn, uint8_t err);
  
  	/** @brief A connection has been disconnected.
  	 *
  	 *  This callback notifies the application that a connection
  	 *  has been disconnected.
  	 *
  	 *  @param conn Connection object.
  	 *  @param reason HCI reason for the disconnection.
  	 */
  	void (*disconnected)(struct bt_conn *conn, uint8_t reason);
  
  	/** @brief LE connection parameter update request.
  	 *
  	 *  This callback notifies the application that a remote device
  	 *  is requesting to update the connection parameters. The
  	 *  application accepts the parameters by returning true, or
  	 *  rejects them by returning false. Before accepting, the
  	 *  application may also adjust the parameters to better suit
  	 *  its needs.
  	 *
  	 *  It is recommended for an application to have just one of these
  	 *  callbacks for simplicity. However, if an application registers
  	 *  multiple it needs to manage the potentially different
  	 *  requirements for each callback. Each callback gets the
  	 *  parameters as returned by previous callbacks, i.e. they are not
  	 *  necessarily the same ones as the remote originally sent.
  	 *
  	 *  @param conn Connection object.
  	 *  @param param Proposed connection parameters.
  	 *
  	 *  @return true to accept the parameters, or false to reject them.
  	 */
  	bool (*le_param_req)(struct bt_conn *conn,
  			     struct bt_le_conn_param *param);
  
  	/** @brief The parameters for an LE connection have been updated.
  	 *
  	 *  This callback notifies the application that the connection
  	 *  parameters for an LE connection have been updated.
  	 *
  	 *  @param conn Connection object.
  	 *  @param interval Connection interval.
  	 *  @param latency Connection latency.
  	 *  @param timeout Connection supervision timeout.
  	 */
  	void (*le_param_updated)(struct bt_conn *conn, uint16_t interval,
  				 uint16_t latency, uint16_t timeout);
  #if defined(CONFIG_BLUETOOTH_SMP)
  	/** @brief Remote Identity Address has been resolved.
  	 *
  	 *  This callback notifies the application that a remote
  	 *  Identity Address has been resolved
  	 *
  	 *  @param conn Connection object.
  	 *  @param rpa Resolvable Private Address.
  	 *  @param identity Identity Address.
  	 */
  	void (*identity_resolved)(struct bt_conn *conn,
  				  const bt_addr_le_t *rpa,
  				  const bt_addr_le_t *identity);
  #endif /* CONFIG_BLUETOOTH_SMP */
  #if defined(CONFIG_BLUETOOTH_SMP) || defined(CONFIG_BLUETOOTH_BREDR)
  	/** @brief The security level of a connection has changed.
  	 *
  	 *  This callback notifies the application that the security level
  	 *  of a connection has changed.
  	 *
  	 *  @param conn Connection object.
  	 *  @param level New security level of the connection.
  	 */
  	void (*security_changed)(struct bt_conn *conn, bt_security_t level);
  #endif /* defined(CONFIG_BLUETOOTH_SMP) || defined(CONFIG_BLUETOOTH_BREDR) */
  	struct bt_conn_cb *_next;
  };
  
  /** @brief Register connection callbacks.
   *
   *  Register callbacks to monitor the state of connections.
   *
   *  @param cb Callback struct.
   */
  void bt_conn_cb_register(struct bt_conn_cb *cb);
  
  /** Authenticated pairing callback structure */
  struct bt_conn_auth_cb {
  	void (*passkey_display)(struct bt_conn *conn, unsigned int passkey);
  	void (*passkey_entry)(struct bt_conn *conn);
  	void (*passkey_confirm)(struct bt_conn *conn, unsigned int passkey);
  	void (*cancel)(struct bt_conn *conn);
  	void (*pairing_confirm)(struct bt_conn *conn);
  #if defined(CONFIG_BLUETOOTH_BREDR)
  	void (*pincode_entry)(struct bt_conn *conn, bool highsec);
  #endif
  };
  
  /** @brief Register authentication callbacks.
   *
   *  Register callbacks to handle authenticated pairing. Passing NULL unregisters
   *  previous callbacks structure.
   *
   *  @param cb Callback struct.
   *
   *  @return Zero on success or negative error code otherwise
   */
  int bt_conn_auth_cb_register(const struct bt_conn_auth_cb *cb);
  
  /** @brief Reply with entered passkey.
   *
   *  This function should be called only after passkey_entry callback from
   *  bt_conn_auth_cb structure was called.
   *
   *  @param conn Connection object.
   *  @param passkey Entered passkey.
   *
   *  @return Zero on success or negative error code otherwise
   */
  int bt_conn_auth_passkey_entry(struct bt_conn *conn, unsigned int passkey);
  
  /** @brief Cancel ongoing authenticated pairing.
   *
   *  This function allows to cancel ongoing authenticated pairing.
   *
   *  @param conn Connection object.
   *
   *  @return Zero on success or negative error code otherwise
   */
  int bt_conn_auth_cancel(struct bt_conn *conn);
  
  /** @brief Reply if passkey was confirmed to match by user.
   *
   *  This function should be called only after passkey_confirm callback from
   *  bt_conn_auth_cb structure was called.
   *
   *  @param conn Connection object.
   *
   *  @return Zero on success or negative error code otherwise
   */
  int bt_conn_auth_passkey_confirm(struct bt_conn *conn);
  
  /** @brief Reply if incoming pairing was confirmed by user.
   *
   *  This function should be called only after pairing_confirm callback from
   *  bt_conn_auth_cb structure was called if user confirmed incoming pairing.
   *
   *  @param conn Connection object.
   *
   *  @return Zero on success or negative error code otherwise
   */
  int bt_conn_auth_pairing_confirm(struct bt_conn *conn);
  
  /** @brief Reply with entered PIN code.
   *
   *  This function should be called only after PIN code callback from
   *  bt_conn_auth_cb structure was called. It's for legacy 2.0 devices.
   *
   *  @param conn Connection object.
   *  @param pin Entered PIN code.
   *
   *  @return Zero on success or negative error code otherwise
   */
  int bt_conn_auth_pincode_entry(struct bt_conn *conn, const char *pin);
  
  /** Connection parameters for BR/EDR connections */
  struct bt_br_conn_param {
  	bool allow_role_switch;
  };
  
  /** Helper to declare BR/EDR connection parameters inline
    *
    * @param role_switch True if role switch is allowed
    */
  #define BT_BR_CONN_PARAM(role_switch) \
  	(&(struct bt_br_conn_param) { \
  		.allow_role_switch = (role_switch), \
  	 })
  
  /** Default BR/EDR connection parameters:
    *   Role switch allowed
    */
  #define BT_BR_CONN_PARAM_DEFAULT BT_BR_CONN_PARAM(true)
  
  
  /** @brief Initiate an BR/EDR connection to a remote device.
   *
   *  Allows initiate new BR/EDR link to remote peer using its address.
   *  Returns a new reference that the the caller is responsible for managing.
   *
   *  @param peer  Remote address.
   *  @param param Initial connection parameters.
   *
   *  @return Valid connection object on success or NULL otherwise.
   */
  struct bt_conn *bt_conn_create_br(const bt_addr_t *peer,
  				  const struct bt_br_conn_param *param);
  
  #ifdef __cplusplus
  }
  #endif
  
  /**
   * @}
   */
  
  #endif /* __BT_CONN_H */
  