As this code is still very new, it has not been heavily optimized yet;
  while it is expected to _eventually_ have better performance than the
  iptables backend, very little performance testing has been done so far. ([#121046](https://github.com/kubernetes/kubernetes/pull/121046), [@danwinship](https://github.com/danwinship))

<pre class="ebnf">
rune_lit         = "'" ( unicode_value | byte_value ) "'" .
unicode_value    = unicode_char | little_u_value | big_u_value | escaped_char .
byte_value       = octal_byte_value | hex_byte_value .
octal_byte_value = `\` octal_digit octal_digit octal_digit .
hex_byte_value   = `\` "x" hex_digit hex_digit .
little_u_value   = `\` "u" hex_digit hex_digit hex_digit hex_digit .