ldns-test-edns -V (return code: 2)
--version error: cannot parse IP address --version
ldns-test-edns -h (return code: 1)
Usage: ldns-test-edns [-i] {ip address}
Tests if the DNS cache at IP address supports EDNS.
if it works, print IP address OK.
-i: print IPs that are OK or print 'off'.
exit value, last IP is 0:OK, 1:fail, 2:net error.