lwIP 2.1.3 Lightweight IP stack

Here is a list of all documented struct and union fields with links to the struct/union documentation for each field:

### - w -

- w : api_msg
- will_msg : mqtt_connect_client_info_t
- will_qos : mqtt_connect_client_info_t
- will_retain : mqtt_connect_client_info_t
- will_topic : mqtt_connect_client_info_t
- write : tftp_context
- write_offset : mdns_outpacket
- writeset : lwip_select_cb