I have upgraded the lwip from 1.3.2 to 1.4.0. In the enclosure you can find my sys_arch.c and sys_arch.h. I am not using mempools, just only malloc and free, #define MEM_LIBC_MALLOC (1) so that you will have to define other functions. The upgrading was easier than to lwip 1.3.2. All stuff around timers can be dropped with NO_SYS 0.
), one tick = 1 ms, if you want to use is with a FreeRTOS, just only rename and functions beginning with UEZ and redefine typedefs to xSemaphoreHandle, xQueueHandle, etc.