glibc 2.2.93 is the one used in Redhat 8.0
When we use that and call gethostbyname_r() with a too small buffer, it no longer returns ERANGE. It now returns EAGAIN!!!
But, older versions (like the ones in redhat 6.0 or 7.3) of glibc obviously sometimes returns EAGAIN when the lookup fails due to normal resolve failures.
So, what the heck shall I check for when I want to know if I need to enlarge the buffer or if the name just doesn't resolve?