text: /*
   * SPDX-FileCopyrightText: 2019-2022 Espressif Systems (Shanghai) CO LTD
   *
   * SPDX-License-Identifier: Apache-2.0
   */
  
  #ifndef _ESP_NETIF_H_
  #define _ESP_NETIF_H_
  
  #include <stdint.h>
  #include "sdkconfig.h"
  #include "esp_wifi_types.h"
  #include "esp_netif_ip_addr.h"
  #include "esp_netif_types.h"
  #include "esp_netif_defaults.h"
  
  #ifdef CONFIG_ETH_ENABLED
  #include "esp_eth_netif_glue.h"
  #endif
  
  //
  // Note: tcpip_adapter legacy API has to be included by default to provide full compatibility
  //  for applications that used tcpip_adapter API without explicit inclusion of tcpip_adapter.h
  //
  #ifdef CONFIG_ESP_NETIF_TCPIP_ADAPTER_COMPATIBLE_LAYER
  #define _ESP_NETIF_SUPPRESS_LEGACY_WARNING_
  #include "tcpip_adapter.h"
  #undef _ESP_NETIF_SUPPRESS_LEGACY_WARNING_
  #endif // CONFIG_ESP_NETIF_TCPIP_ADAPTER_COMPATIBLE_LAYER
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /**
   * @defgroup ESP_NETIF_INIT_API ESP-NETIF Initialization API
   * @brief Initialization and deinitialization of underlying TCP/IP stack and esp-netif instances
   *
   */
  
  /** @addtogroup ESP_NETIF_INIT_API
   * @{
   */
  
  /**
   * @brief  Initialize the underlying TCP/IP stack
   *
   * @return
   *         - ESP_OK on success
   *         - ESP_FAIL if initializing failed
  
   * @note This function should be called exactly once from application code, when the application starts up.
   */
  esp_err_t esp_netif_init(void);
  
  /**
   * @brief  Deinitialize the esp-netif component (and the underlying TCP/IP stack)
   *
   *          Note: Deinitialization is not supported yet
   *
   * @return
   *         - ESP_ERR_INVALID_STATE if esp_netif not initialized
   *         - ESP_ERR_NOT_SUPPORTED otherwise
   */
  esp_err_t esp_netif_deinit(void);
  
  /**
   * @brief   Creates an instance of new esp-netif object based on provided config
   *
   * @param[in]     esp_netif_config pointer esp-netif configuration
   *
   * @return
   *         - pointer to esp-netif object on success
   *         - NULL otherwise
   */
  esp_netif_t *esp_netif_new(const esp_netif_config_t *esp_netif_config);
  
  /**
   * @brief   Destroys the esp_netif object
   *
   * @param[in]  esp_netif pointer to the object to be deleted
   */
  void esp_netif_destroy(esp_netif_t *esp_netif);
  
  /**
   * @brief   Configures driver related options of esp_netif object
   *
   * @param[inout]  esp_netif pointer to the object to be configured
   * @param[in]     driver_config pointer esp-netif io driver related configuration
   * @return
   *         - ESP_OK on success
   *         - ESP_ERR_ESP_NETIF_INVALID_PARAMS if invalid parameters provided
   *
   */
  esp_err_t esp_netif_set_driver_config(esp_netif_t *esp_netif,
                                        const esp_netif_driver_ifconfig_t *driver_config);
  
  /**
   * @brief   Attaches esp_netif instance to the io driver handle
   *
   * Calling this function enables connecting specific esp_netif object
   * with already initialized io driver to update esp_netif object with driver
   * specific configuration (i.e. calls post_attach callback, which typically
   * sets io driver callbacks to esp_netif instance and starts the driver)
   *
   * @param[inout]  esp_netif pointer to esp_netif object to be attached
   * @param[in]  driver_handle pointer to the driver handle
   * @return
   *         - ESP_OK on success
   *         - ESP_ERR_ESP_NETIF_DRIVER_ATTACH_FAILED if driver's pot_attach callback failed
   */
  esp_err_t esp_netif_attach(esp_netif_t *esp_netif, esp_netif_iodriver_handle driver_handle);
  
  /**
   * @}
   */
  
  /**
   * @defgroup ESP_NETIF_DATA_IO_API ESP-NETIF Input Output API
   * @brief Input and Output functions to pass data packets from communication media (IO driver)
   * to TCP/IP stack.
   *
   * These functions are usually not directly called from user code, but installed, or registered
   * as callbacks in either IO driver on one hand or TCP/IP stack on the other. More specifically
   * esp_netif_receive is typically called from io driver on reception callback to input the packets
   * to TCP/IP stack. Similarly esp_netif_transmit is called from the TCP/IP stack whenever
   * a packet ought to output to the communication media.
   *
   * @note These IO functions are registerd (installed) automatically for default interfaces
   * (interfaces with the keys such as WIFI_STA_DEF, WIFI_AP_DEF, ETH_DEF). Custom interface
   * has to register these IO functions when creating interface using @ref esp_netif_new
   *
   */
  
  /** @addtogroup ESP_NETIF_DATA_IO_API
   * @{
   */
  
  /**
   * @brief  Passes the raw packets from communication media to the appropriate TCP/IP stack
   *
   * This function is called from the configured (peripheral) driver layer.
   * The data are then forwarded as frames to the TCP/IP stack.
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[in]  buffer Received data
   * @param[in]  len Length of the data frame
   * @param[in]  eb Pointer to internal buffer (used in Wi-Fi driver)
   *
   * @return
   *         - ESP_OK
   */
  esp_err_t esp_netif_receive(esp_netif_t *esp_netif, void *buffer, size_t len, void *eb);
  
  /**
   * @}
   */
  
  /**
   * @defgroup ESP_NETIF_L2_TAP_CTRL ESP-NETIF L2 TAP Control API
   * @brief Functions to control access to ESP-NETIF Data link layer
   */
  
  /** @addtogroup ESP_NETIF_L2_TAP_CTRL
   * @{
   */
  
  /**
   * @brief Add transmit hook callback function reference into ESP-NETIF. This callback function
   *        is then called just prior the ESP-NETIF passes data to network driver.
   *
   * @param[in] esp_netif Handle to esp-netif instance
   * @param[in] hook_fn reference to transmit hook call-back function
   * @return
   *         - ESP_OK - success
   *         - ESP_ERR_INVALID_ARG
   */
  esp_err_t esp_netif_transmit_hook_attach(esp_netif_t *esp_netif, void *hook_fn);
  
  /**
   * @brief Add post transmit hook callback function reference into ESP-NETIF. This callback function
   *        is then called just after the ESP-NETIF passes data to network driver.
   *
   * @note Intention of this function is either to release resources allocated by transmit hook function
   *       or for other use cases such as time stamping, etc.
   *
   * @param[in] esp_netif Handle to esp-netif instance
   * @param[in] hook_fn reference to post transmit hook call-back function
   * @return
   *         - ESP_OK - success
   *         - ESP_ERR_INVALID_ARG
   */
  esp_err_t esp_netif_post_transmit_hook_attach(esp_netif_t *esp_netif, void *hook_fn);
  
  /**
   * @brief Add receive hook callback function reference into ESP-NETIF. This callback function
   *        is then called when network driver receives data.
   *
   * @param[in] esp_netif Handle to esp-netif instance
   * @param[in] hook_fn reference to receive hook callback function
   * @return
   *         - ESP_OK - success
   *         - ESP_ERR_INVALID_ARG
   */
  esp_err_t esp_netif_recv_hook_attach(esp_netif_t *esp_netif, void *hook_fn);
  
  /**
   * @brief Removes reference to previously attachhed transmit hook callback function
   *
   * @param[in] esp_netif Handle to esp-netif instance
   * @return
   *         - ESP_OK - success
   *         - ESP_ERR_INVALID_ARG
   */
  esp_err_t esp_netif_transmit_hook_detach(esp_netif_t *esp_netif);
  
  /**
   * @brief Removes reference to previously attachhed posttransmit hook callback function
   *
   * @param[in] esp_netif Handle to esp-netif instance
   * @return
   *         - ESP_OK - success
   *         - ESP_ERR_INVALID_ARG
   */
  esp_err_t esp_netif_post_transmit_hook_detach(esp_netif_t *esp_netif);
  
  /**
   * @brief Removes reference to previously attachhed receive hook callback function
   *
   * @param[in] esp_netif Handle to esp-netif instance
   * @return
   *         - ESP_OK - success
   *         - ESP_ERR_INVALID_ARG
   */
  esp_err_t esp_netif_recv_hook_detach(esp_netif_t *esp_netif);
  
  /**
   * @}
   */
  
  /**
   * @defgroup ESP_NETIF_LIFECYCLE ESP-NETIF Lifecycle control
   * @brief These APIS define basic building blocks to control network interface lifecycle, i.e.
   * start, stop, set_up or set_down. These functions can be directly used as event handlers
   * registered to follow the events from communication media.
   */
  
  /** @addtogroup ESP_NETIF_LIFECYCLE
   * @{
   */
  
  /**
   * @brief Default building block for network interface action upon IO driver start event
   * Creates network interface, if AUTOUP enabled turns the interface on,
   * if DHCPS enabled starts dhcp server
   *
   * @note This API can be directly used as event handler
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param base
   * @param event_id
   * @param data
   */
  void esp_netif_action_start(void *esp_netif, esp_event_base_t base, int32_t event_id, void *data);
  
  /**
   * @brief Default building block for network interface action upon IO driver stop event
   *
   * @note This API can be directly used as event handler
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param base
   * @param event_id
   * @param data
   */
  void esp_netif_action_stop(void *esp_netif, esp_event_base_t base, int32_t event_id, void *data);
  
  /**
   * @brief Default building block for network interface action upon IO driver connected event
   *
   * @note This API can be directly used as event handler
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param base
   * @param event_id
   * @param data
   */
  void esp_netif_action_connected(void *esp_netif, esp_event_base_t base, int32_t event_id, void *data);
  
  /**
   * @brief Default building block for network interface action upon IO driver disconnected event
   *
   * @note This API can be directly used as event handler
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param base
   * @param event_id
   * @param data
   */
  void esp_netif_action_disconnected(void *esp_netif, esp_event_base_t base, int32_t event_id, void *data);
  
  /**
   * @brief Default building block for network interface action upon network got IP event
   *
   * @note This API can be directly used as event handler
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param base
   * @param event_id
   * @param data
   */
  void esp_netif_action_got_ip(void *esp_netif, esp_event_base_t base, int32_t event_id, void *data);
  
  /**
   * @brief Default building block for network interface action upon IPv6 multicast group join
   *
   * @note This API can be directly used as event handler
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param base
   * @param event_id
   * @param data
   */
  void esp_netif_action_join_ip6_multicast_group(void *esp_netif, esp_event_base_t base, int32_t event_id, void *data);
  
  /**
   * @brief Default building block for network interface action upon IPv6 multicast group leave
   *
   * @note This API can be directly used as event handler
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param base
   * @param event_id
   * @param data
   */
  void esp_netif_action_leave_ip6_multicast_group(void *esp_netif, esp_event_base_t base, int32_t event_id, void *data);
  
  /**
   * @brief Default building block for network interface action upon IPv6 address added by the underlying stack
   *
   * @note This API can be directly used as event handler
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param base
   * @param event_id
   * @param data
   */
  void esp_netif_action_add_ip6_address(void *esp_netif, esp_event_base_t base, int32_t event_id, void *data);
  
  /**
   * @brief Default building block for network interface action upon IPv6 address removed by the underlying stack
   *
   * @note This API can be directly used as event handler
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param base
   * @param event_id
   * @param data
   */
  void esp_netif_action_remove_ip6_address(void *esp_netif, esp_event_base_t base, int32_t event_id, void *data);
  
  /**
   * @}
   */
  
  /**
   * @defgroup ESP_NETIF_GET_SET ESP-NETIF Runtime configuration
   * @brief Getters and setters for various TCP/IP related parameters
   */
  
  /** @addtogroup ESP_NETIF_GET_SET
   * @{
   */
  
  /**
   * @brief Set the mac address for the interface instance
  
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[in]  mac Desired mac address for the related network interface
   * @return
   *         - ESP_OK - success
   *         - ESP_ERR_ESP_NETIF_IF_NOT_READY - interface status error
   *         - ESP_ERR_NOT_SUPPORTED - mac not supported on this interface
   */
  esp_err_t esp_netif_set_mac(esp_netif_t *esp_netif, uint8_t mac[]);
  
  /**
   * @brief Get the mac address for the interface instance
  
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[out]  mac Resultant mac address for the related network interface
   * @return
   *         - ESP_OK - success
   *         - ESP_ERR_ESP_NETIF_IF_NOT_READY - interface status error
   *         - ESP_ERR_NOT_SUPPORTED - mac not supported on this interface
   */
  esp_err_t esp_netif_get_mac(esp_netif_t *esp_netif, uint8_t mac[]);
  
  /**
   * @brief  Set the hostname of an interface
   *
   * The configured hostname overrides the default configuration value CONFIG_LWIP_LOCAL_HOSTNAME.
   * Please note that when the hostname is altered after interface started/connected the changes
   * would only be reflected once the interface restarts/reconnects
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[in]   hostname New hostname for the interface. Maximum length 32 bytes.
   *
   * @return
   *         - ESP_OK - success
   *         - ESP_ERR_ESP_NETIF_IF_NOT_READY - interface status error
   *         - ESP_ERR_ESP_NETIF_INVALID_PARAMS - parameter error
   */
  esp_err_t esp_netif_set_hostname(esp_netif_t *esp_netif, const char *hostname);
  
  /**
   * @brief  Get interface hostname.
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[out]   hostname Returns a pointer to the hostname. May be NULL if no hostname is set. If set non-NULL, pointer remains valid (and string may change if the hostname changes).
   *
   * @return
   *         - ESP_OK - success
   *         - ESP_ERR_ESP_NETIF_IF_NOT_READY - interface status error
   *         - ESP_ERR_ESP_NETIF_INVALID_PARAMS - parameter error
   */
  esp_err_t esp_netif_get_hostname(esp_netif_t *esp_netif, const char **hostname);
  
  /**
   * @brief  Test if supplied interface is up or down
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   *
   * @return
   *         - true - Interface is up
   *         - false - Interface is down
   */
  bool esp_netif_is_netif_up(esp_netif_t *esp_netif);
  
  /**
   * @brief  Get interface's IP address information
   *
   * If the interface is up, IP information is read directly from the TCP/IP stack.
   * If the interface is down, IP information is read from a copy kept in the ESP-NETIF instance
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[out]  ip_info If successful, IP information will be returned in this argument.
   *
   * @return
   *         - ESP_OK
   *         - ESP_ERR_ESP_NETIF_INVALID_PARAMS
   */
  esp_err_t esp_netif_get_ip_info(esp_netif_t *esp_netif, esp_netif_ip_info_t *ip_info);
  
  /**
   * @brief  Get interface's old IP information
   *
   * Returns an "old" IP address previously stored for the interface when the valid IP changed.
   *
   * If the IP lost timer has expired (meaning the interface was down for longer than the configured interval)
   * then the old IP information will be zero.
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[out]  ip_info If successful, IP information will be returned in this argument.
   *
   * @return
   *         - ESP_OK
   *         - ESP_ERR_ESP_NETIF_INVALID_PARAMS
   */
  esp_err_t esp_netif_get_old_ip_info(esp_netif_t *esp_netif, esp_netif_ip_info_t *ip_info);
  
  /**
   * @brief  Set interface's IP address information
   *
   * This function is mainly used to set a static IP on an interface.
   *
   * If the interface is up, the new IP information is set directly in the TCP/IP stack.
   *
   * The copy of IP information kept in the ESP-NETIF instance is also updated (this
   * copy is returned if the IP is queried while the interface is still down.)
   *
   * @note DHCP client/server must be stopped (if enabled for this interface) before setting new IP information.
   *
   * @note Calling this interface for may generate a SYSTEM_EVENT_STA_GOT_IP or SYSTEM_EVENT_ETH_GOT_IP event.
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[in] ip_info IP information to set on the specified interface
   *
   * @return
   *      - ESP_OK
   *      - ESP_ERR_ESP_NETIF_INVALID_PARAMS
   *      - ESP_ERR_ESP_NETIF_DHCP_NOT_STOPPED If DHCP server or client is still running
   */
  esp_err_t esp_netif_set_ip_info(esp_netif_t *esp_netif, const esp_netif_ip_info_t *ip_info);
  
  /**
   * @brief  Set interface old IP information
   *
   * This function is called from the DHCP client (if enabled), before a new IP is set.
   * It is also called from the default handlers for the SYSTEM_EVENT_STA_CONNECTED and SYSTEM_EVENT_ETH_CONNECTED events.
   *
   * Calling this function stores the previously configured IP, which can be used to determine if the IP changes in the future.
   *
   * If the interface is disconnected or down for too long, the "IP lost timer" will expire (after the configured interval) and set the old IP information to zero.
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[in]  ip_info Store the old IP information for the specified interface
   *
   * @return
   *         - ESP_OK
   *         - ESP_ERR_ESP_NETIF_INVALID_PARAMS
   */
  esp_err_t esp_netif_set_old_ip_info(esp_netif_t *esp_netif, const esp_netif_ip_info_t *ip_info);
  
  /**
   * @brief  Get net interface index from network stack implementation
   *
   * @note This index could be used in `setsockopt()` to bind socket with multicast interface
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   *
   * @return
   *         implementation specific index of interface represented with supplied esp_netif
   */
  int esp_netif_get_netif_impl_index(esp_netif_t *esp_netif);
  
  /**
   * @brief  Get net interface name from network stack implementation
   *
   * @note This name could be used in `setsockopt()` to bind socket with appropriate interface
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[out]  name Interface name as specified in underlying TCP/IP stack. Note that the
   * actual name will be copied to the specified buffer, which must be allocated to hold
   * maximum interface name size (6 characters for lwIP)
   *
   * @return
   *         - ESP_OK
   *         - ESP_ERR_ESP_NETIF_INVALID_PARAMS
  */
  esp_err_t esp_netif_get_netif_impl_name(esp_netif_t *esp_netif, char* name);
  
  /**
   * @}
   */
  
  /**
   * @defgroup ESP_NETIF_NET_DHCP ESP-NETIF DHCP Settings
   * @brief Network stack related interface to DHCP client and server
   */
  
  /** @addtogroup ESP_NETIF_NET_DHCP
   * @{
   */
  
  /**
   * @brief  Set or Get DHCP server option
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[in] opt_op ESP_NETIF_OP_SET to set an option, ESP_NETIF_OP_GET to get an option.
   * @param[in] opt_id Option index to get or set, must be one of the supported enum values.
   * @param[inout] opt_val Pointer to the option parameter.
   * @param[in] opt_len Length of the option parameter.
   *
   * @return
   *         - ESP_OK
   *         - ESP_ERR_ESP_NETIF_INVALID_PARAMS
   *         - ESP_ERR_ESP_NETIF_DHCP_ALREADY_STOPPED
   *         - ESP_ERR_ESP_NETIF_DHCP_ALREADY_STARTED
   */
  esp_err_t
  esp_netif_dhcps_option(esp_netif_t *esp_netif, esp_netif_dhcp_option_mode_t opt_op, esp_netif_dhcp_option_id_t opt_id,
                         void *opt_val, uint32_t opt_len);
  
  /**
   * @brief  Set or Get DHCP client option
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[in] opt_op ESP_NETIF_OP_SET to set an option, ESP_NETIF_OP_GET to get an option.
   * @param[in] opt_id Option index to get or set, must be one of the supported enum values.
   * @param[inout] opt_val Pointer to the option parameter.
   * @param[in] opt_len Length of the option parameter.
   *
   * @return
   *         - ESP_OK
   *         - ESP_ERR_ESP_NETIF_INVALID_PARAMS
   *         - ESP_ERR_ESP_NETIF_DHCP_ALREADY_STOPPED
   *         - ESP_ERR_ESP_NETIF_DHCP_ALREADY_STARTED
   */
  esp_err_t
  esp_netif_dhcpc_option(esp_netif_t *esp_netif, esp_netif_dhcp_option_mode_t opt_op, esp_netif_dhcp_option_id_t opt_id,
                         void *opt_val, uint32_t opt_len);
  
  /**
   * @brief Start DHCP client (only if enabled in interface object)
   *
   * @note The default event handlers for the SYSTEM_EVENT_STA_CONNECTED and SYSTEM_EVENT_ETH_CONNECTED events call this function.
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   *
   * @return
   *         - ESP_OK
   *         - ESP_ERR_ESP_NETIF_INVALID_PARAMS
   *         - ESP_ERR_ESP_NETIF_DHCP_ALREADY_STARTED
   *         - ESP_ERR_ESP_NETIF_DHCPC_START_FAILED
   */
  esp_err_t esp_netif_dhcpc_start(esp_netif_t *esp_netif);
  
  /**
   * @brief  Stop DHCP client (only if enabled in interface object)
   *
   * @note Calling action_netif_stop() will also stop the DHCP Client if it is running.
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   *
   * @return
   *      - ESP_OK
   *      - ESP_ERR_ESP_NETIF_INVALID_PARAMS
   *      - ESP_ERR_ESP_NETIF_DHCP_ALREADY_STOPPED
   *      - ESP_ERR_ESP_NETIF_IF_NOT_READY
   */
  esp_err_t esp_netif_dhcpc_stop(esp_netif_t *esp_netif);
  
  /**
   * @brief  Get DHCP client status
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[out] status If successful, the status of DHCP client will be returned in this argument.
   *
   * @return
   *         - ESP_OK
   */
  esp_err_t esp_netif_dhcpc_get_status(esp_netif_t *esp_netif, esp_netif_dhcp_status_t *status);
  
  /**
   * @brief  Get DHCP Server status
   *
   * @param[in]   esp_netif Handle to esp-netif instance
   * @param[out]  status If successful, the status of the DHCP server will be returned in this argument.
   *
   * @return
   *         - ESP_OK
   */
  esp_err_t esp_netif_dhcps_get_status(esp_netif_t *esp_netif, esp_netif_dhcp_status_t *status);
  
  /**
   * @brief  Start DHCP server (only if enabled in interface object)
   *
   * @param[in]   esp_netif Handle to esp-netif instance
   *
   * @return
   *         - ESP_OK
   *         - ESP_ERR_ESP_NETIF_INVALID_PARAMS
   *         - ESP_ERR_ESP_NETIF_DHCP_ALREADY_STARTED
   */
  esp_err_t esp_netif_dhcps_start(esp_netif_t *esp_netif);
  
  /**
   * @brief  Stop DHCP server (only if enabled in interface object)
   *
   * @param[in]   esp_netif Handle to esp-netif instance
   *
   * @return
   *      - ESP_OK
   *      - ESP_ERR_ESP_NETIF_INVALID_PARAMS
   *      - ESP_ERR_ESP_NETIF_DHCP_ALREADY_STOPPED
   *      - ESP_ERR_ESP_NETIF_IF_NOT_READY
   */
  esp_err_t esp_netif_dhcps_stop(esp_netif_t *esp_netif);
  
  /**
   * @}
   */
  
  /**
   * @defgroup ESP_NETIF_NET_DNS ESP-NETIF DNS Settings
   * @brief Network stack related interface to NDS
   */
  
  /** @addtogroup ESP_NETIF_NET_DNS
   * @{
   */
  
  /**
   * @brief  Set DNS Server information
   *
   * This function behaves differently if DHCP server or client is enabled
   *
   *   If DHCP client is enabled, main and backup DNS servers will be updated automatically
   *   from the DHCP lease if the relevant DHCP options are set. Fallback DNS Server is never updated from the DHCP lease
   *   and is designed to be set via this API.
   *   If DHCP client is disabled, all DNS server types can be set via this API only.
   *
   *   If DHCP server is enabled, the Main DNS Server setting is used by the DHCP server to provide a DNS Server option
   *   to DHCP clients (Wi-Fi stations).
   *   - The default Main DNS server is typically the IP of the Wi-Fi AP interface itself.
   *   - This function can override it by setting server type ESP_NETIF_DNS_MAIN.
   *   - Other DNS Server types are not supported for the Wi-Fi AP interface.
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[in]  type Type of DNS Server to set: ESP_NETIF_DNS_MAIN, ESP_NETIF_DNS_BACKUP, ESP_NETIF_DNS_FALLBACK
   * @param[in]  dns  DNS Server address to set
   *
   * @return
   *      - ESP_OK on success
   *      - ESP_ERR_ESP_NETIF_INVALID_PARAMS invalid params
   */
  esp_err_t esp_netif_set_dns_info(esp_netif_t *esp_netif, esp_netif_dns_type_t type, esp_netif_dns_info_t *dns);
  
  /**
   * @brief  Get DNS Server information
   *
   * Return the currently configured DNS Server address for the specified interface and Server type.
   *
   * This may be result of a previous call to esp_netif_set_dns_info(). If the interface's DHCP client is enabled,
   * the Main or Backup DNS Server may be set by the current DHCP lease.
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[in]  type Type of DNS Server to get: ESP_NETIF_DNS_MAIN, ESP_NETIF_DNS_BACKUP, ESP_NETIF_DNS_FALLBACK
   * @param[out] dns  DNS Server result is written here on success
   *
   * @return
   *      - ESP_OK on success
   *      - ESP_ERR_ESP_NETIF_INVALID_PARAMS invalid params
   */
  esp_err_t esp_netif_get_dns_info(esp_netif_t *esp_netif, esp_netif_dns_type_t type, esp_netif_dns_info_t *dns);
  
  /**
   * @}
   */
  
  /**
   * @defgroup ESP_NETIF_NET_IP ESP-NETIF IP address related interface
   * @brief Network stack related interface to IP
   */
  
  /** @addtogroup ESP_NETIF_NET_IP
   * @{
   */
  #if CONFIG_LWIP_IPV6
  /**
   * @brief  Create interface link-local IPv6 address
   *
   * Cause the TCP/IP stack to create a link-local IPv6 address for the specified interface.
   *
   * This function also registers a callback for the specified interface, so that if the link-local address becomes
   * verified as the preferred address then a SYSTEM_EVENT_GOT_IP6 event will be sent.
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   *
   * @return
   *         - ESP_OK
   *         - ESP_ERR_ESP_NETIF_INVALID_PARAMS
   */
  esp_err_t esp_netif_create_ip6_linklocal(esp_netif_t *esp_netif);
  
  /**
   * @brief  Get interface link-local IPv6 address
   *
   * If the specified interface is up and a preferred link-local IPv6 address
   * has been created for the interface, return a copy of it.
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[out] if_ip6 IPv6 information will be returned in this argument if successful.
   *
   * @return
   *      - ESP_OK
   *      - ESP_FAIL If interface is down, does not have a link-local IPv6 address,
   *        or the link-local IPv6 address is not a preferred address.
   */
  esp_err_t esp_netif_get_ip6_linklocal(esp_netif_t *esp_netif, esp_ip6_addr_t *if_ip6);
  
  /**
   * @brief  Get interface global IPv6 address
   *
   * If the specified interface is up and a preferred global IPv6 address
   * has been created for the interface, return a copy of it.
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[out] if_ip6 IPv6 information will be returned in this argument if successful.
   *
   * @return
   *      - ESP_OK
   *      - ESP_FAIL If interface is down, does not have a global IPv6 address,
   *        or the global IPv6 address is not a preferred address.
   */
  esp_err_t esp_netif_get_ip6_global(esp_netif_t *esp_netif, esp_ip6_addr_t *if_ip6);
  
  /**
   * @brief  Get all IPv6 addresses of the specified interface
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   * @param[out] if_ip6 Array of IPv6 addresses will be copied to the argument
   *
   * @return
   *      number of returned IPv6 addresses
   */
  int esp_netif_get_all_ip6(esp_netif_t *esp_netif, esp_ip6_addr_t if_ip6[]);
  #endif
  
  /**
   * @brief Sets IPv4 address to the specified octets
   *
   * @param[out] addr IP address to be set
   * @param a the first octet (127 for IP 127.0.0.1)
   * @param b
   * @param c
   * @param d
   */
  void esp_netif_set_ip4_addr(esp_ip4_addr_t *addr, uint8_t a, uint8_t b, uint8_t c, uint8_t d);
  
  
  /**
   * @brief Converts numeric IP address into decimal dotted ASCII representation.
   *
   * @param addr ip address in network order to convert
   * @param buf target buffer where the string is stored
   * @param buflen length of buf
   * @return either pointer to buf which now holds the ASCII
   *         representation of addr or NULL if buf was too small
   */
  char *esp_ip4addr_ntoa(const esp_ip4_addr_t *addr, char *buf, int buflen);
  
  /**
   * @brief Ascii internet address interpretation routine
   * The value returned is in network order.
   *
   * @param addr IP address in ascii representation (e.g. "127.0.0.1")
   * @return ip address in network order
  */
  uint32_t esp_ip4addr_aton(const char *addr);
  
  /**
   * @brief Converts Ascii internet IPv4 address into esp_ip4_addr_t
   *
   * @param[in] src IPv4 address in ascii representation (e.g. "127.0.0.1")
   * @param[out] dst Address of the target esp_ip4_addr_t structure to receive converted address
   * @return
   *         - ESP_OK on success
   *         - ESP_FAIL if conversion failed
   *         - ESP_ERR_INVALID_ARG if invalid parameter is passed into
   */
  esp_err_t esp_netif_str_to_ip4(const char *src, esp_ip4_addr_t *dst);
  
  /**
   * @brief Converts Ascii internet IPv6 address into esp_ip4_addr_t
   * Zeros in the IP address can be stripped or completely ommited: "2001:db8:85a3:0:0:0:2:1" or "2001:db8::2:1")
   *
   * @param[in] src IPv6 address in ascii representation (e.g. ""2001:0db8:85a3:0000:0000:0000:0002:0001")
   * @param[out] dst Address of the target esp_ip6_addr_t structure to receive converted address
   * @return
   *         - ESP_OK on success
   *         - ESP_FAIL if conversion failed
   *         - ESP_ERR_INVALID_ARG if invalid parameter is passed into
   */
  esp_err_t esp_netif_str_to_ip6(const char *src, esp_ip6_addr_t *dst);
  
  /**
   * @}
   */
  
  /**
   * @defgroup ESP_NETIF_CONVERT ESP-NETIF Conversion utilities
   * @brief  ESP-NETIF conversion utilities to related keys, flags, implementation handle
   */
  
  /** @addtogroup ESP_NETIF_CONVERT
   * @{
   */
  
  /**
   * @brief Gets media driver handle for this esp-netif instance
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   *
   * @return opaque pointer of related IO driver
   */
  esp_netif_iodriver_handle esp_netif_get_io_driver(esp_netif_t *esp_netif);
  
  /**
   * @brief Searches over a list of created objects to find an instance with supplied if key
   *
   * @param if_key Textual description of network interface
   *
   * @return Handle to esp-netif instance
   */
  esp_netif_t *esp_netif_get_handle_from_ifkey(const char *if_key);
  
  /**
   * @brief Returns configured flags for this interface
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   *
   * @return Configuration flags
   */
  esp_netif_flags_t esp_netif_get_flags(esp_netif_t *esp_netif);
  
  /**
   * @brief Returns configured interface key for this esp-netif instance
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   *
   * @return Textual description of related interface
   */
  const char *esp_netif_get_ifkey(esp_netif_t *esp_netif);
  
  /**
   * @brief Returns configured interface type for this esp-netif instance
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   *
   * @return Enumerated type of this interface, such as station, AP, ethernet
   */
  const char *esp_netif_get_desc(esp_netif_t *esp_netif);
  
  /**
   * @brief Returns configured routing priority number
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   *
   * @return Integer representing the instance's route-prio, or -1 if invalid paramters
   */
  int esp_netif_get_route_prio(esp_netif_t *esp_netif);
  
  /**
   * @brief Returns configured event for this esp-netif instance and supplied event type
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   *
   * @param event_type (either get or lost IP)
   *
   * @return specific event id which is configured to be raised if the interface lost or acquired IP address
   *         -1 if supplied event_type is not known
   */
  int32_t esp_netif_get_event_id(esp_netif_t *esp_netif, esp_netif_ip_event_type_t event_type);
  
  /**
   * @}
   */
  
  /**
   * @defgroup ESP_NETIF_LIST ESP-NETIF List of interfaces
   * @brief  APIs to enumerate all registered interfaces
   */
  
  /** @addtogroup ESP_NETIF_LIST
   * @{
   */
  
  /**
   * @brief Iterates over list of interfaces. Returns first netif if NULL given as parameter
   *
   * @param[in]  esp_netif Handle to esp-netif instance
   *
   * @return First netif from the list if supplied parameter is NULL, next one otherwise
   */
  esp_netif_t *esp_netif_next(esp_netif_t *esp_netif);
  
  /**
   * @brief Returns number of registered esp_netif objects
   *
   * @return Number of esp_netifs
   */
  size_t esp_netif_get_nr_of_ifs(void);
  
  /**
   * @brief increase the reference counter of net stack buffer
   *
   * @param[in]  netstack_buf the net stack buffer
   *
   */
  void esp_netif_netstack_buf_ref(void *netstack_buf);
  
  /**
   * @brief free the netstack buffer
   *
   * @param[in]  netstack_buf the net stack buffer
   *
   */
  void esp_netif_netstack_buf_free(void *netstack_buf);
  
  /**
   * @}
   */
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /*  _ESP_NETIF_H_ */
  