<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
  </head>
  <body text="#000000" bgcolor="#FFFFFF">
    <div class="moz-cite-prefix">On 30/10/2019 02:33, Aaron D. Gifford
      wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAGDxMR5s-Z81k9Bg5BBTnhfE2Zs_+3LGoBPsQ6P4OJDJFLrsdg@mail.gmail.com">On
      a FreeBSD system running PowerDNS authoritative server 4.2.0, I
      noticed this:<br>
      <div>
        <div><br>
        </div>
        <div># sockstat -4<br>
          USER     COMMAND    PID   FD PROTO  LOCAL ADDRESS        
          FOREIGN ADDRESS      <br>
          root     pdns_serve 40055 4  udp4   <a
            href="http://192.168.50.12:53" moz-do-not-send="true">192.168.50.12:53</a>
              *:*<br>
          root     pdns_serve 40055 6  tcp4   <a
            href="http://192.168.50.12:53" moz-do-not-send="true">192.168.50.12:53</a>
              *:*<br>
          root     pdns_serve 40055 8  tcp4   <a
            href="http://192.168.50.12:55401" moz-do-not-send="true">192.168.50.12:55401</a>
           <a href="http://127.0.0.1:3306" moz-do-not-send="true">127.0.0.1:3306</a><br>
          root     pdns_serve 40055 9  tcp4   <a
            href="http://192.168.50.12:54277" moz-do-not-send="true">192.168.50.12:54277</a>
           <a href="http://127.0.0.1:3306" moz-do-not-send="true">127.0.0.1:3306</a><br>
          root     pdns_serve 40055 16 udp4   <a
            href="http://192.168.50.12:19413" moz-do-not-send="true">192.168.50.12:19413</a>
           *:*<br>
          ...<br>
          <br>
        </div>
        <div>Why is it listening on UDP port 19413?  I thought I'd
          disabled various subsystems that might want to listen on a TCP
          or UDP port.</div>
      </div>
    </blockquote>
    <p>If you restart pdns I think you'll find it binds to a different
      random port, which almost certainly means it's a socket which has
      been created for the purpose of sending *outbound* UDP packets.  I
      see the same here:</p>
    <p><tt>$ sudo netstat -naup | grep pdns</tt><tt><br>
      </tt><tt>udp        0      0 0.0.0.0:53             
        0.0.0.0:*                           17497/pdns_server</tt><tt><br>
      </tt><tt>udp        0      0 0.0.0.0:12579          
        0.0.0.0:*                           17497/pdns_server</tt><tt><br>
      </tt><tt>udp6       0      0 :::53                  
        :::*                                17497/pdns_server</tt><tt><br>
      </tt><tt>udp6       0      0 :::11846               
        :::*                                17497/pdns_server</tt></p>
    <p><tt>$ sudo systemctl restart pdns</tt><tt><br>
      </tt></p>
    <p><tt>$ sudo netstat -naup | grep pdns</tt><tt><br>
      </tt><tt>udp        0      0 0.0.0.0:53             
        0.0.0.0:*                           12560/pdns_server</tt><tt><br>
      </tt><tt>udp        0      0 0.0.0.0:17662          
        0.0.0.0:*                           12560/pdns_server</tt><tt><br>
      </tt><tt>udp6       0      0 :::53                  
        :::*                                12560/pdns_server</tt><tt><br>
      </tt><tt>udp6       0      0 :::16544               
        :::*                                12560/pdns_server</tt></p>
    <p>Although pdns auth no longer has a recursor option, and I have
      expand-alias turned off, I suspect it is for sending NOTIFY
      packets.</p>
    <p>Anyway, it's not a listening port, so you don't need to worry
      about it.<br>
    </p>
  </body>
</html>