mod_s2s_keepalive: Isolate source host of pings The incoming_s2s table is not restricted to the current virtualhost so this prevents opening more connections than what's needed. Also prevents useless double sending of one whitespace per local host.

<tr>
  <th>What is {x} {op} {y}?</th><td>
    <input name="captcha_challenge" type="hidden" value="{challenge}">
    <input name="captcha_reply" pattern="[0-9]+" required type="number">
  </td></tr>