module Seahorse::Util

def host_label?(str)

Other tags:
    See: https://tools.ietf.org/html/rfc1123#page-13 -
    See: https://tools.ietf.org/html/rfc3986#section-3.2.2 -
def host_label?(str)
  str =~ /^(?!-)[a-zA-Z0-9-]{1,63}(?<!-)$/
end