make install: download, compile, install lwip2

make latestmaster: download latest lwip2, compile, install

make latestupstream: download latest lwip2 and latest upstream lwIP, compile, install

make download: download lwIP-2 builder

make clean: clean builder only

glue and lwIP debug options are in builder/glue/gluedebug.h

MSS values are in builder/Makefile.arduino

MSS values in boards.txt are only informative