For more details about Mbed TLS's migration from version 2.x to version 3.0 or greater, please refer to the `official guide <https://github.com/espressif/mbedtls/blob/9bb5effc3298265f829878825d9bd38478e67514/docs/3.0-migration-guide.md>`__.
- Direct access to fields of structures (``struct`` types) declared in public headers is no longer supported.
- Appropriate accessor functions (getter/setter) must be used for the same. A temporary workaround would be to use ``MBEDTLS_PRIVATE`` macro (**not recommended**).
- For more details, refer to the `official guide <https://github.com/espressif/mbedtls/blob/9bb5effc3298265f829878825d9bd38478e67514/docs/3.0-migration-guide.md#most-structure-fields-are-now-private>`__.
- The functions ``mbedtls_*_ret()`` (related to MD, SHA, RIPEMD, RNG, HMAC modules) was renamed to replace the corresponding functions without ``_ret`` appended and updated return value.
- For more details, refer to the `official guide <https://github.com/espressif/mbedtls/blob/9bb5effc3298265f829878825d9bd38478e67514/docs/3.0-migration-guide.md#deprecated-functions-were-removed-from-hashing-modules>`__.
Following are some of the important config options deprecated by this update. The configs related to and/or dependent on these have also been deprecated.
-``MBEDTLS_SSL_PROTO_SSL3`` : Support for SSL 3.0
-``MBEDTLS_SSL_PROTO_TLS1`` : Support for TLS 1.0
-``MBEDTLS_SSL_PROTO_TLS1_1``: Support for TLS 1.1
-``MBEDTLS_SSL_PROTO_DTLS`` : Support for DTLS 1.1 (Only DTLS 1.2 is supported now)
-``MBEDTLS_DES_C`` : Support for 3DES ciphersuites
-``MBEDTLS_RC4_MODE`` : Support for RC4-based ciphersuites
This list includes only major options configurable through ``idf.py menuconfig``. For more details on deprecated options, refer to the `official guide <https://github.com/espressif/mbedtls/blob/9bb5effc3298265f829878825d9bd38478e67514/docs/3.0-migration-guide.md#most-structure-fields-are-now-private>`__.
The Diffie-Hellman Key Exchange modes have now been disabled by default due to security risks (see warning text `here <https://github.com/espressif/mbedtls/blob/9bb5effc3298265f829878825d9bd38478e67514/include/mbedtls/dhm.h#L20>`__). Related configs are given below:
During the initial step of the handshake (i.e., ``client_hello``), the server selects a cipher from the list that the client publishes. As the DHE_PSK/DHE_RSA ciphers have now been disabled by the above change, the server would fall back to an alternative cipher; if in a rare case, it does not support any other cipher, the handshake would fail. To retrieve the list of ciphers supported by the server, one must attempt to connect with the server with a specific cipher from the client-side. Few utilities can help do this, e.g., ``sslscan``.
- The :cpp:func:`esp_crt_bundle_set()` API now requires one additional argument named ``bundle_size``. The return type of the API has also been changed to :cpp:type:`esp_err_t` from ``void``.
- The function :cpp:func:`esp_https_ota` now requires pointer to :cpp:type:`esp_https_ota_config_t` as argument instead of pointer to :cpp:type:`esp_http_client_config_t`.
The :cpp:type:`esp_tls_t` has now been made completely private. You cannot access its internal structures directly. Any necessary data that needs to be obtained from the ESP-TLS handle can be done through respective getter/setter functions. If there is a requirement of a specific getter/setter function, please raise an `issue <https://github.com/espressif/esp-idf/issues>`__ on ESP-IDF.
- The function :cpp:func:`esp_tls_conn_http_new` has now been termed as deprecated. Please use the alternative function :cpp:func:`esp_tls_conn_http_new_sync` (or its asynchronous :cpp:func:`esp_tls_conn_http_new_async`). Note that the alternatives need an additional parameter :cpp:type:`esp_tls_t`, which has to be initialized using the :cpp:func:`esp_tls_init` function.
-``http_server.h`` header is no longer available in ``esp_http_server``. Please use ``esp_http_server.h`` instead.
ESP HTTP Client
---------------
Breaking Changes (Summary)
~~~~~~~~~~~~~~~~~~~~~~~~~~
- The functions :cpp:func:`esp_http_client_read` and :cpp:func:`esp_http_client_fetch_headers` now return an additional return value ``-ESP_ERR_HTTP_EAGAIN`` for timeout errors - call timed-out before any data was ready.
- The function :cpp:func:`esp_transport_read` now returns ``0`` for a connection timeout and ``< 0`` for other errors. Please refer :cpp:enum:`esp_tcp_transport_err_t` for all possible return values.
-:cpp:type:`esp_mqtt_client_config_t` no longer supports the ``user_context`` field. Please use :cpp:func:`esp_mqtt_client_register_event` instead for registering an event handler; the last argument ``event_handler_arg`` can be used to pass user context to the handler.
The ESP-IDF component ``freemodbus`` has been removed from ESP-IDF and is supported as a separate component. Additional information for the ``ESP-Modbus`` component can be found in the separate repository:
The ``esp-modbus`` component can be found in `ESP Component Registry <https://components.espressif.com/component/espressif/esp-modbus>`__. Refer to `component manager documentation <https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/tools/idf-component-manager.html>`__ for more information on how to set up the component manager.
For applications targeting v4.x releases of ESP-IDF that need to use new ``esp-modbus`` component, adding the component manager manifest file ``idf_component.yml`` will be sufficient to pull in the new component. However, users should also exclude the legacy ``freemodbus`` component from the build. This can be achieved using the statement below in the project's ``CMakeLists.txt``:
