ESP-NETIF ========= The purpose of ESP-NETIF library is twofold: - It provides an abstraction layer for the application on top of the TCP/IP stack. This will allow applications to choose between IP stacks in the future. - The APIs it provides are thread safe, even if the underlying TCP/IP stack APIs are not. ESP-IDF currently implements ESP-NETIF for the lwIP TCP/IP stack only. However, the adapter itself is TCP/IP implementation agnostic and different implementations are possible. Some ESP-NETIF API functions are intended to be called by application code, for example to get/set interface IP addresses, configure DHCP. Other functions are intended for internal ESP-IDF use by the network driver layer. In many cases, applications do not need to call ESP-NETIF APIs directly as they are called from the default network event handlers. ESP-NETIF architecture ====================== .. code-block:: text | (A) USER CODE | | | .............| init settings events | . +----------------------------------------+ . . | * . . | * --------+ +===========================+ * +-----------------------+ | | new/config get/set | * | | | | |...*.....| init | | |---------------------------| * | | init | | |**** | | start |********| event handler |*********| DHCP | stop | | | | | | |---------------------------| | | | | | | NETIF | +-----| | | +-----------------+ | | glue|----<---| esp_netif_transmit |--<------| netif_output | | | | | | | | | | |---->---| esp_netif_receive |-->------| netif_input | | | | | | + ----------------+ | | |....<...| esp_netif_free_rx_buffer |...<.....| packet buffer | +-----| | | | | | | | | (D) | (B) | | (C) | +-----------------------+ --------+ +===========================+ communication NETWORK STACK DRIVER ESP-NETIF Data and event flow in the diagram ---------------------------------- * ``........`` Initialization line from user code to ESP-NETIF and communication driver * ``--<--->--`` Data packets going from communication media to TCP/IP stack and back * ``********`` Events aggregated in ESP-NETIF propagates to driver, user code and network stack * ``|`` User settings and runtime configuration ESP-NETIF interaction --------------------- A) User code, boiler plate ^^^^^^^^^^^^^^^^^^^^^^^^^^ Overall application interaction with a specific IO driver for communication media and configured TCP/IP network stack is abstracted using ESP-NETIF APIs and outlined as below: A) Initialization code 1) Initializes IO driver 2) Creates a new instance of ESP-NETIF and configure with * ESP-NETIF specific options (flags, behaviour, name) * Network stack options (netif init and input functions, not publicly available) * IO driver specific options (transmit, free rx buffer functions, IO driver handle) 3) Attaches the IO driver handle to the ESP-NETIF instance created in the above steps 4) Configures event handlers * use default handlers for common interfaces defined in IO drivers; or define a specific handlers for customised behaviour/new interfaces * register handlers for app related events (such as IP lost/acquired) B) Interaction with network interfaces using ESP-NETIF API * Getting and setting TCP/IP related parameters (DHCP, IP, etc) * Receiving IP events (connect/disconnect) * Controlling application lifecycle (set interface up/down) Please note that the initialization code as well as registering event handlers for default interfaces, such as WiFi softAP and WiFi station, are provided as a separate APIs (for example ``esp_netif_create_default_wifi_ap()`` and ``esp_netif_create_default_wifi_sta()``) to facilitate simple startup code for most applications. B) Communication driver, IO driver, media driver ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Communication driver plays these two important roles in relation with ESP-NETIF: 1) Event handlers: Define behaviour patterns of interaction with ESP-NETIF (for example: ethernet link-up -> turn netif on) 2) Glue IO layer: Adapts the input/output functions to use ESP-NETIF transmit, receive and free receive buffer * Installs driver_transmit to appropriate ESP-NETIF object, so that outgoing packets from network stack are passed to the IO driver * Calls ``esp_netif_receive()`` to pass incoming data to network stack C) ESP-NETIF, former tcpip_adapter ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ESP-NETIF is an intermediary between an IO driver and a network stack, connecting packet data path between these two. As that it provides a set of interfaces for attaching a driver to ESP-NETIF object (runtime) and configuring a network stack (compile time). In addition to that a set of API is provided to control network interface lifecycle and its TCP/IP properties. As an overview, the ESP-NETIF public interface could be divided into these 6 groups: 1) Initialization APIs (to create and configure ESP-NETIF instance) 2) Input/Output API (for passing data between IO driver and network stack) 3) Event or Action API * Used for network interface lifecycle management * ESP-NETIF provides building blocks for designing event handlers 4) Setters and Getters for basic network interface properties 5) Network stack abstraction: enabling user interaction with TCP/IP stack * Set interface up or down * DHCP server and client API * DNS API 6) Driver conversion utilities D) Network stack ^^^^^^^^^^^^^^^^ Network stack has no public interaction with application code with regard to public interfaces and shall be fully abstracted by ESP-NETIF API. API Reference ------------- .. include:: /_build/inc/esp_netif.inc