title: LWIP lockup on STM32
body: <p>I have been having an issue in my project with LWIP. I am using a ST32F4 MCU and running with no OS. The network seems to run fine, the protocols all work, but then (usually a day or two later) the stack just stops running. It seems to happen when trying to make a new connection, but I can't confirm that because I haven't been able to locate what is causing it in the code.</p>
  
  <p>Has anyone else come across this issue? I think it may be the same as <a href="https://stackoverflow.com/questions/45935885/lwip-stm32-http-requests-failing">this guy</a>.</p>