From here LWIP V2.

Last version on LWIP 4.1 (4_1_1 DEVEL).

uart: fix send possible buffer overflow when logging to uart.

The overflow would be temporary and nothing harmful would happen, but
some logging would get lost.

Remove a few functions from IRAM that do not really need to be in there.

uart bridge: try to reduce latency.

Start sending to the network immediately when data arrives at the UART.
Don't wait for the next slow timer to fire.

Makefile: add release target.

io: fix simple digital not autostarted.

id: fix off-by-one.

uart: enable selecting polarity of UART input and output pins.

use flag-set or flag-unset:
    "uart0-tx-inv"
    "uart0-rx-inv"
    "uart1-tx-inv"

This comes in handy e.g. for driving led pixels without the need to add
a hardware inverter.

Release 18.