Comment 14 for bug 1949643

Test Steps from Debian bug, for reference.

- 1. Configure rules files:

cat <<EOF4 >/etc/iptables/rules.v4
# Generated by iptables-save v1.8.7 on Wed Nov 3 20:43:56 2021
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -s 1.0.0.1/32 -p icmp -j DROP
COMMIT
# Completed on Wed Nov 3 20:43:56 2021
EOF4

cat <<EOF6 >/etc/iptables/rules.v6
# Generated by ip6tables-save v1.8.7 on Wed Nov 3 20:43:56 2021
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -s 2606:4700:4700::1001/128 -p icmp -j DROP
COMMIT
# Completed on Wed Nov 3 20:43:56 2021
EOF6

 - 2. Flush existing rules:

iptables -F
ip6tables -F

 - 3. Add rules for 1.1.1.1:

iptables -A INPUT -p icmp -s 1.1.1.1 -j DROP
ip6tables -A INPUT -p icmp -s 2606:4700:4700::1111 -j DROP

- 4. Check rules for 1.1.1.1 are in:

iptables -nL | grep -e 1.1.1.1 -e 1.0.0.1
ip6tables -nL | grep -e 2606:4700:4700::1111 -e 2606:4700:4700::1001

- 5. Start iptables-persistent scripts:

netfilter-persistent start

Default behavior:

- 6. Check rules for 1.0.0.1 are in (rules for 1.1.1.1 are gone)

iptables -nL | grep -e 1.1.1.1 -e 1.0.0.1
ip6tables -nL | grep -e 2606:4700:4700::1111 -e 2606:4700:4700::1001

Optional behavior:

- 7. Enable the new options:

sed -i '/RESTORE_NOFLUSH/ s/^# //' /etc/default/netfilter-persistent

- 8. Repeat steps 2-5

- 9. Check rules for 1.0.0.1 _and_ 1.1.1.1 are in (rules for 1.1.1.1 are kept)

iptables -nL | grep -e 1.1.1.1 -e 1.0.0.1
ip6tables -nL | grep -e 2606:4700:4700::1111 -e 2606:4700:4700::1001