iptables-repro-2.sh

#!/usr/bin/env bash

failed=false

function felix () {
    while true; do
        echo -n a
        iptables-restore --noflush --verbose <<EOF
*filter
:felix -
--append felix -m comment --comment "FELIX-A"
--delete dummy-chain 1
COMMIT
EOF
        echo -n A
        echo -n b
        iptables-restore --noflush --verbose <<EOF
*filter
:felix -
--append felix -m comment --comment "FELIX-B"
--append dummy-chain
COMMIT
EOF
        echo -n B
        if iptables-save | grep -q FELIX-A; then
          echo
          echo "FELIX-B update was clobbered"
          failed=true
          return 1
        fi
        echo -n C
    done
}

function kube () {
    while ! ${failed}; do
       echo -n k
       iptables-restore --noflush --verbose 2>/dev/null <<EOF
*filter
:kube -
COMMIT
EOF
        if [ $? == "0" ]; then 
          echo -n K
        else
          echo -n Z
        fi
    done
}

iptables-restore --noflush --verbose <<EOF
*filter
:dummy-chain -
-A dummy-chain
COMMIT
EOF


kube &
kube_pid=$!
felix; kill $kube_pid