lwIP needs you to provide some time base.
That depends on you using NO_SYS=1 (usually bare metal) or NO_SYS=0 (OS
The fact that you are getting the linker to signal a missing file is an
indication that you are missing part of what lwIP expects, according to
the way you configured it.
I ported to bare metal (NO_SYS=1) so I can't help you with FreeRTOS, you
can check out the wiki or the already running FreeRTOS ports around.
The wiki is at wikia: http://lwip.wikia.com/
PS: Search the list, I think this has been answered before.
lwip-users mailing listaddress@hiddenhttps://lists.nongnu.org/mailman/listinfo/lwip-users