IPAddr#link_local?

# File tmp/rubies/ruby-3.4.1/lib/ipaddr.rb, line 321
def link_local?
  case @family
  when Socket::AF_INET
    @addr & 0xffff0000 == 0xa9fe0000 # 169.254.0.0/16
  when Socket::AF_INET6
    @addr & 0xffc0_0000_0000_0000_0000_0000_0000_0000 == 0xfe80_0000_0000_0000_0000_0000_0000_0000 || # fe80::/10
      (@addr & 0xffff_0000_0000 == 0xffff_0000_0000 && (
        @addr & 0xffff0000 == 0xa9fe0000 # ::ffff:169.254.0.0/16
      ))
  else
    raise AddressFamilyError, "unsupported address family"
  end
end