2.9. Blocking external access to the NodePort service on a specific host interface

Procedure

1. Change the NODEPORT variable to the host port number assigned to your Kubernetes NodePort service by running the following command:

   # export NODEPORT=30700

2. Change the INTERFACE_IP value to the IP address from the host interface that you want to block. For example:

   # export INTERFACE_IP=192.168.150.33

3. Insert a new rule in the nat table PREROUTING chain to drop all packets that match the destination port and IP address. For example:

   $ sudo nft -a insert rule ip nat PREROUTING tcp dport $NODEPORT ip daddr $INTERFACE_IP drop

4. List the new rule by running the following command:

   $ sudo nft -a list chain ip nat PREROUTING
   table ip nat {
   	chain PREROUTING { # handle 1
   		type nat hook prerouting priority dstnat; policy accept;
   		tcp dport 30700 ip daddr 192.168.150.33 drop # handle 134
   		counter packets 108 bytes 18074 jump OVN-KUBE-ETP # handle 116
   		counter packets 108 bytes 18074 jump OVN-KUBE-EXTERNALIP # handle 114
   		counter packets 108 bytes 18074 jump OVN-KUBE-NODEPORT # handle 112
   	}
   }

   注記

   Note the handle number of the newly added rule. You need to remove the handle number in the following step.

5. Remove the custom rule with the following sample command:

   $ sudo nft -a delete rule ip nat PREROUTING handle 134