Merge branch 'examples/getaddrinfo_af_unspec' into 'master'

feat(examples): Added wrapper for getaddrinfo to handle AF_UNSPEC

Closes IDFGH-12201

See merge request espressif/esp-idf!33234

docs/en/api-guides/lwip.rst

@@ -474,6 +474,8 @@ The number of IP addresses returned by network database APIs such as ``getaddrin
 
 In the implementation of ``getaddrinfo()``, the canonical name is not available. Therefore, the ``ai_canonname`` field of the first returned ``addrinfo`` structure will always refer to the ``nodename`` argument or a string with the same contents.
 
+The ``getaddrinfo()`` system call in lwIP within ESP-IDF has a limitation when using ``AF_UNSPEC``, as it defaults to returning only an IPv4 address in dual stack mode. This can cause issues in IPv6-only networks. To handle this, a workaround involves making two sequential calls to ``getaddrinfo()``: the first with AF_INET to query for IPv4 addresses, and the second with AF_INET6 to retrieve IPv6 addresses. To address this, the custom ``esp_getaddrinfo()`` function has been added to the lwIP port layer to handle both IPv4 and IPv6 addresses when AF_UNSPEC is used. The :ref:`CONFIG_LWIP_USE_ESP_GETADDRINFO` option, available when both IPv4 and IPv6 are enabled, controls whether ``esp_getaddrinfo()`` or the default lwIP implementation is used. It is disabled by default.
+
 Calling ``send()`` or ``sendto()`` repeatedly on a UDP socket may eventually fail with ``errno`` equal to ``ENOMEM``. This failure occurs due to the limitations of buffer sizes in the lower-layer network interface drivers. If all driver transmit buffers are full, the UDP transmission will fail. For applications that transmit a high volume of UDP datagrams and aim to avoid any dropped datagrams by the sender, it is advisable to implement error code checking and employ a retransmission mechanism with a short delay.
 
 .. only:: esp32