lwIP 2.1.0 Lightweight IP stack

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

### - o -

- offset : api_msg
- oid : snmp_node , snmp_varbind
- old_address : netif_ext_callback_args_t::ipv4_changed_s , netif_ext_callback_args_t::ipv6_set_s
- old_state : netif_ext_callback_args_t::ipv6_addr_state_changed_s
- op_completed : netconn
- open : tftp_context
- original : pbuf_custom_ref
- output : mqtt_client_s , netif
- output_ip6 : netif