for VS/NAT when the load balancer receives packets from real
servers but the connection entries don't exist.
+pmtu_disc - BOOLEAN
+ 0 - disabled
+ not 0 - enabled (default)
+
+ By default, reject with FRAG_NEEDED all DF packets that exceed
+ the PMTU, irrespective of the forwarding method. For TUN method
+ the flag can be disabled to fragment such packets.
+
secure_tcp - INTEGER
0 - disabled (default)